feat: add core persistence model

Directory.Packages.props

@@ -11,9 +11,18 @@
       <PrivateAssets>all</PrivateAssets>
     </PackageVersion>
     <PackageVersion Include="Microsoft.AspNetCore.OpenApi" Version="10.0.10" />
+    <PackageVersion Include="Microsoft.EntityFrameworkCore" Version="10.0.10" />
+    <PackageVersion Include="Microsoft.EntityFrameworkCore.Design" Version="10.0.10">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageVersion>
+    <PackageVersion Include="Microsoft.EntityFrameworkCore.Relational" Version="10.0.10" />
+    <PackageVersion Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="10.0.10" />
     <PackageVersion Include="Microsoft.Extensions.Hosting" Version="10.0.10" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.8.1" />
     <PackageVersion Include="Microsoft.OpenApi" Version="2.11.0" />
+    <PackageVersion Include="Npgsql" Version="10.0.3" />
+    <PackageVersion Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="10.0.3" />
     <PackageVersion Include="Scalar.AspNetCore" Version="2.16.16" />
     <PackageVersion Include="xunit" Version="2.9.3" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="3.1.4">

Tiku.Api/Program.cs

@@ -21,7 +21,7 @@ var summaries = new[]
 
 app.MapGet("/weatherforecast", () =>
 {
-    var forecast =  Enumerable.Range(1, 5).Select(index =>
+    var forecast = Enumerable.Range(1, 5).Select(index =>
         new WeatherForecast
         (
             DateOnly.FromDateTime(DateTime.Now.AddDays(index)),

Tiku.Application/Class1.cs

@@ -1,6 +0,0 @@
-namespace Tiku.Application;
-
-public class Class1
-{
-
-}

Tiku.DbMigrator/DesignTimeTikuDbContextFactory.cs

@@ -0,0 +1,22 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Design;
+using Tiku.Infrastructure.Persistence;
+
+namespace Tiku.DbMigrator;
+
+public sealed class DesignTimeTikuDbContextFactory : IDesignTimeDbContextFactory<TikuDbContext>
+{
+    public TikuDbContext CreateDbContext(string[] args)
+    {
+        var connectionString =
+            Environment.GetEnvironmentVariable("DATABASE_URL") ??
+            "Host=localhost;Database=tiku;Username=postgres";
+
+        var options = new DbContextOptionsBuilder<TikuDbContext>()
+            .UseNpgsql(connectionString, npgsql =>
+                npgsql.MigrationsAssembly(typeof(TikuDbContext).Assembly.FullName))
+            .Options;
+
+        return new TikuDbContext(options);
+    }
+}

Tiku.DbMigrator/Program.cs

@@ -1,2 +1,20 @@
-// See https://aka.ms/new-console-template for more information
+using Microsoft.EntityFrameworkCore;
-Console.WriteLine("Hello, World!");
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Tiku.Infrastructure;
+using Tiku.Infrastructure.Persistence;
+
+var builder = Host.CreateApplicationBuilder(args);
+var connectionString =
+    builder.Configuration.GetConnectionString("Database") ??
+    Environment.GetEnvironmentVariable("DATABASE_URL") ??
+    throw new InvalidOperationException(
+        "Database connection is required. Configure ConnectionStrings:Database or DATABASE_URL.");
+
+builder.Services.AddInfrastructure(connectionString);
+
+using var host = builder.Build();
+await using var scope = host.Services.CreateAsyncScope();
+var dbContext = scope.ServiceProvider.GetRequiredService<TikuDbContext>();
+await dbContext.Database.MigrateAsync();

Tiku.DbMigrator/Tiku.DbMigrator.csproj

@@ -4,6 +4,14 @@
     <ProjectReference Include="..\Tiku.Infrastructure\Tiku.Infrastructure.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Design">
+      <IncludeAssets>all</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+    <PackageReference Include="Microsoft.Extensions.Hosting" />
+  </ItemGroup>
+
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>net10.0</TargetFramework>

Tiku.Domain/Catalog/CatalogEntities.cs

@@ -0,0 +1,126 @@
+using System.Text.Json;
+using Tiku.Domain.Common;
+
+namespace Tiku.Domain.Catalog;
+
+public sealed class Region : AuditableTenantEntity
+{
+    public string? LegacyId { get; set; }
+    public string Name { get; set; } = string.Empty;
+    public string? Code { get; set; }
+    public string? ShortName { get; set; }
+    public string? FullName { get; set; }
+    public string? Icon { get; set; }
+    public string? Pinyin { get; set; }
+    public int SortOrder { get; set; }
+    public bool IsHot { get; set; }
+    public bool IsActive { get; set; } = true;
+    public JsonElement Config { get; set; } = JsonDefaults.Object();
+}
+
+public sealed class RegionModule : AuditableTenantEntity
+{
+    public Guid? RegionId { get; set; }
+    public string? LegacyId { get; set; }
+    public string Name { get; set; } = string.Empty;
+    public string? Type { get; set; }
+    public string? Icon { get; set; }
+    public string? Color { get; set; }
+    public string? TextColor { get; set; }
+    public string? Description { get; set; }
+    public string? Route { get; set; }
+    public int SortOrder { get; set; }
+    public bool IsPrimarySchoolModule { get; set; }
+    public bool IsActive { get; set; } = true;
+}
+
+public sealed class ModuleNode : AuditableTenantEntity
+{
+    public Guid? RegionId { get; set; }
+    public Guid? ModuleId { get; set; }
+    public Guid? ParentId { get; set; }
+    public string? LegacyId { get; set; }
+    public string? LegacyParentId { get; set; }
+    public string? LegacyModuleId { get; set; }
+    public ModuleNodeType Type { get; set; } = ModuleNodeType.Custom;
+    public string Name { get; set; } = string.Empty;
+    public string? Path { get; set; }
+    public int SortOrder { get; set; }
+    public bool IsActive { get; set; } = true;
+    public JsonElement Metadata { get; set; } = JsonDefaults.Object();
+}
+
+public enum ModuleNodeType
+{
+    Category,
+    Subject,
+    Chapter,
+    Paper,
+    School,
+    Major,
+    Custom
+}
+
+public sealed class School : AuditableTenantEntity
+{
+    public Guid? RegionId { get; set; }
+    public Guid? ModuleId { get; set; }
+    public string? LegacyId { get; set; }
+    public string Name { get; set; } = string.Empty;
+    public string? ProfessionalExamDate { get; set; }
+    public JsonElement Metadata { get; set; } = JsonDefaults.Object();
+}
+
+public sealed class Major : AuditableTenantEntity
+{
+    public Guid? RegionId { get; set; }
+    public Guid? SchoolId { get; set; }
+    public string? LegacyId { get; set; }
+    public string Name { get; set; } = string.Empty;
+    public string? Description { get; set; }
+    public string? StudyTips { get; set; }
+    public int SortOrder { get; set; }
+    public bool IsActive { get; set; } = true;
+}
+
+public sealed class Subject : AuditableTenantEntity
+{
+    public Guid? RegionId { get; set; }
+    public Guid? ModuleId { get; set; }
+    public Guid? SchoolId { get; set; }
+    public Guid? MajorId { get; set; }
+    public Guid? NodeId { get; set; }
+    public string? LegacyId { get; set; }
+    public string Name { get; set; } = string.Empty;
+    public SubjectType? Type { get; set; }
+    public JsonElement MajorLegacyIds { get; set; } = JsonDefaults.Array();
+    public string? Icon { get; set; }
+    public string? Description { get; set; }
+    public JsonElement Stats { get; set; } = JsonDefaults.Object();
+    public int SortOrder { get; set; }
+    public bool IsActive { get; set; } = true;
+}
+
+public enum SubjectType
+{
+    Cultural,
+    Professional
+}
+
+public sealed class Category : AuditableTenantEntity
+{
+    public Guid? SubjectId { get; set; }
+    public Guid? NodeId { get; set; }
+    public string? LegacyId { get; set; }
+    public string Name { get; set; } = string.Empty;
+    public CategoryType? CategoryType { get; set; }
+    public int SortOrder { get; set; }
+    public int? SvipQuestionLimit { get; set; }
+    public bool IsActive { get; set; } = true;
+}
+
+public enum CategoryType
+{
+    Chapter,
+    Paper
+}

Tiku.Domain/Class1.cs

@@ -1,6 +0,0 @@
-namespace Tiku.Domain;
-
-public class Class1
-{
-
-}

Tiku.Domain/Common/Entity.cs

@@ -0,0 +1,46 @@
+using System.Text.Json;
+
+namespace Tiku.Domain.Common;
+
+public abstract class Entity
+{
+    public Guid Id { get; set; } = Guid.NewGuid();
+}
+
+public interface IHasTimestamps
+{
+    DateTimeOffset CreatedAt { get; set; }
+    DateTimeOffset UpdatedAt { get; set; }
+}
+
+public abstract class AuditableEntity : Entity, IHasTimestamps
+{
+    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
+    public DateTimeOffset UpdatedAt { get; set; } = DateTimeOffset.UtcNow;
+}
+
+public abstract class TenantEntity : Entity
+{
+    public Guid TenantId { get; set; }
+}
+
+public abstract class AuditableTenantEntity : TenantEntity, IHasTimestamps
+{
+    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
+    public DateTimeOffset UpdatedAt { get; set; } = DateTimeOffset.UtcNow;
+}
+
+public static class JsonDefaults
+{
+    public static JsonElement Object()
+    {
+        using var document = JsonDocument.Parse("{}");
+        return document.RootElement.Clone();
+    }
+
+    public static JsonElement Array()
+    {
+        using var document = JsonDocument.Parse("[]");
+        return document.RootElement.Clone();
+    }
+}

Tiku.Domain/Identity/StudentProfile.cs

@@ -0,0 +1,20 @@
+using System.Text.Json;
+using Tiku.Domain.Common;
+
+namespace Tiku.Domain.Identity;
+
+public sealed class StudentProfile : AuditableTenantEntity
+{
+    public Guid UserId { get; set; }
+    public string? LegacyUserId { get; set; }
+    public Guid? RegionId { get; set; }
+    public Guid? SelectedSchoolId { get; set; }
+    public Guid? SelectedMajorId { get; set; }
+    public int QuestionsAnsweredToday { get; set; }
+    public int MasteredWordsCount { get; set; }
+    public DateOnly? LastCheckInDate { get; set; }
+    public JsonElement Stats { get; set; } = JsonDefaults.Object();
+    public JsonElement Progress { get; set; } = JsonDefaults.Object();
+    public JsonElement ModuleSelections { get; set; } = JsonDefaults.Object();
+    public JsonElement RecentActivities { get; set; } = JsonDefaults.Array();
+}

Tiku.Domain/Identity/User.cs

@@ -0,0 +1,20 @@
+using System.Text.Json;
+using Tiku.Domain.Common;
+
+namespace Tiku.Domain.Identity;
+
+public sealed class User : AuditableEntity
+{
+    public string? LegacyId { get; set; }
+    public string? Username { get; set; }
+    public string? Email { get; set; }
+    public string? Phone { get; set; }
+    public string? Name { get; set; }
+    public string? AvatarUrl { get; set; }
+    public string PrimaryRole { get; set; } = "student";
+    public int Score { get; set; }
+    public DateTimeOffset? LastSeenAt { get; set; }
+    public string? LegacyPasswordHash { get; set; }
+    public bool PasswordMigrationRequired { get; set; }
+    public JsonElement RawProfile { get; set; } = JsonDefaults.Object();
+}

Tiku.Domain/Identity/UserIdentity.cs

@@ -0,0 +1,16 @@
+using System.Text.Json;
+using Tiku.Domain.Common;
+
+namespace Tiku.Domain.Identity;
+
+public sealed class UserIdentity : AuditableEntity
+{
+    public Guid UserId { get; set; }
+    public string Provider { get; set; } = string.Empty;
+    public string ProviderSubject { get; set; } = string.Empty;
+    public string? UnionId { get; set; }
+    public string? OpenId { get; set; }
+    public string? Phone { get; set; }
+    public string? Email { get; set; }
+    public JsonElement SecretPayload { get; set; } = JsonDefaults.Object();
+}

Tiku.Domain/Learning/LearningEntities.cs

@@ -0,0 +1,64 @@
+using System.Text.Json;
+using Tiku.Domain.Common;
+
+namespace Tiku.Domain.Learning;
+
+public sealed class PracticeSession : TenantEntity
+{
+    public Guid UserId { get; set; }
+    public string Mode { get; set; } = "chapter";
+    public string? TargetType { get; set; }
+    public Guid? TargetId { get; set; }
+    public DateTimeOffset StartedAt { get; set; } = DateTimeOffset.UtcNow;
+    public DateTimeOffset? FinishedAt { get; set; }
+    public JsonElement Metadata { get; set; } = JsonDefaults.Object();
+}
+
+public sealed class AnswerRecord : TenantEntity
+{
+    public Guid UserId { get; set; }
+    public Guid? QuestionId { get; set; }
+    public Guid? QuestionVersionId { get; set; }
+    public Guid? PracticeSessionId { get; set; }
+    public string? LegacyId { get; set; }
+    public string? LegacyQuestionId { get; set; }
+    public string? LegacyCategoryId { get; set; }
+    public JsonElement SelectedOptions { get; set; } = JsonDefaults.Array();
+    public string? AnswerText { get; set; }
+    public bool? IsCorrect { get; set; }
+    public DateTimeOffset AnsweredAt { get; set; } = DateTimeOffset.UtcNow;
+    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
+}
+
+public sealed class FavoriteQuestion
+{
+    public Guid TenantId { get; set; }
+    public Guid UserId { get; set; }
+    public Guid QuestionId { get; set; }
+    public string Source { get; set; } = "imported";
+    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
+}
+
+public sealed class WrongQuestion
+{
+    public Guid TenantId { get; set; }
+    public Guid UserId { get; set; }
+    public Guid QuestionId { get; set; }
+    public int WrongCount { get; set; } = 1;
+    public DateTimeOffset LastWrongAt { get; set; } = DateTimeOffset.UtcNow;
+    public DateTimeOffset? ResolvedAt { get; set; }
+}
+
+public sealed class RecentPractice : AuditableTenantEntity
+{
+    public Guid? UserId { get; set; }
+    public string? LegacyId { get; set; }
+    public string? PracticeType { get; set; }
+    public string? TargetLegacyId { get; set; }
+    public string? TargetName { get; set; }
+    public int Progress { get; set; }
+    public string? Color { get; set; }
+    public DateTimeOffset? LastAccessAt { get; set; }
+    public DateTimeOffset? LastPracticeAt { get; set; }
+    public JsonElement Metadata { get; set; } = JsonDefaults.Object();
+}

Tiku.Domain/QuestionBanks/QuestionEntities.cs

@@ -0,0 +1,71 @@
+using System.Text.Json;
+using Tiku.Domain.Common;
+
+namespace Tiku.Domain.QuestionBanks;
+
+public sealed class QuestionBank : AuditableTenantEntity
+{
+    public Guid? RegionId { get; set; }
+    public string Name { get; set; } = string.Empty;
+    public QuestionBankScope SourceScope { get; set; } = QuestionBankScope.Tenant;
+    public QuestionBankStatus Status { get; set; } = QuestionBankStatus.Active;
+    public JsonElement Metadata { get; set; } = JsonDefaults.Object();
+}
+
+public enum QuestionBankScope
+{
+    Platform,
+    Tenant
+}
+
+public enum QuestionBankStatus
+{
+    Active,
+    Archived
+}
+
+public sealed class Question : AuditableTenantEntity
+{
+    public Guid? QuestionBankId { get; set; }
+    public Guid? SubjectId { get; set; }
+    public Guid? CategoryId { get; set; }
+    public Guid? NodeId { get; set; }
+    public string? LegacyId { get; set; }
+    public string? LegacySubjectId { get; set; }
+    public string? LegacyCategoryId { get; set; }
+    public string? LegacyNodeId { get; set; }
+    public string Type { get; set; } = "choice";
+    public string? TypeLabel { get; set; }
+    public int? Difficulty { get; set; }
+    public JsonElement Tags { get; set; } = JsonDefaults.Array();
+    public string? MediaUrl { get; set; }
+    public bool HasVideoExplanation { get; set; }
+    public QuestionStatus Status { get; set; } = QuestionStatus.Published;
+    public Guid? CurrentVersionId { get; set; }
+}
+
+public enum QuestionStatus
+{
+    Draft,
+    Published,
+    Archived
+}
+
+public sealed class QuestionVersion : Entity
+{
+    public Guid TenantId { get; set; }
+    public Guid QuestionId { get; set; }
+    public int VersionNo { get; set; } = 1;
+    public string? Content { get; set; }
+    public JsonElement Options { get; set; } = JsonDefaults.Array();
+    public int? CorrectOptionIndex { get; set; }
+    public JsonElement CorrectOptionIndices { get; set; } = JsonDefaults.Array();
+    public string? AnswerText { get; set; }
+    public string? Explanation { get; set; }
+    public JsonElement SubQuestions { get; set; } = JsonDefaults.Array();
+    public string? CodeLang { get; set; }
+    public string? CodeTemplate { get; set; }
+    public string? SourceHash { get; set; }
+    public Guid? CreatedBy { get; set; }
+    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
+}

Tiku.Domain/Tenancy/Tenant.cs

@@ -0,0 +1,40 @@
+using System.Text.Json;
+using Tiku.Domain.Common;
+
+namespace Tiku.Domain.Tenancy;
+
+public sealed class Tenant : AuditableEntity
+{
+    public string Slug { get; set; } = string.Empty;
+    public string Name { get; set; } = string.Empty;
+    public string? LegalName { get; set; }
+    public TenantStatus Status { get; set; } = TenantStatus.Active;
+    public TenantMode Mode { get; set; } = TenantMode.Saas;
+    public BillingStatus BillingStatus { get; set; } = BillingStatus.Trial;
+    public Guid? OwnerUserId { get; set; }
+    public string? LegacyId { get; set; }
+    public JsonElement Metadata { get; set; } = JsonDefaults.Object();
+}
+
+public enum TenantStatus
+{
+    Draft,
+    Active,
+    Suspended,
+    Archived
+}
+
+public enum TenantMode
+{
+    PlatformOwned,
+    Saas,
+    Dedicated
+}
+
+public enum BillingStatus
+{
+    Trial,
+    Active,
+    PastDue,
+    Cancelled
+}

Tiku.Domain/Tenancy/TenantMembership.cs

@@ -0,0 +1,32 @@
+using System.Text.Json;
+using Tiku.Domain.Common;
+
+namespace Tiku.Domain.Tenancy;
+
+public sealed class TenantMembership : AuditableTenantEntity
+{
+    public Guid UserId { get; set; }
+    public TenantRole Role { get; set; } = TenantRole.Student;
+    public MembershipStatus Status { get; set; } = MembershipStatus.Active;
+    public JsonElement Permissions { get; set; } = JsonDefaults.Object();
+    public string? LegacyRole { get; set; }
+}
+
+public enum TenantRole
+{
+    PlatformAdmin,
+    TenantOwner,
+    TenantAdmin,
+    TenantOperator,
+    Teacher,
+    Sales,
+    Agent,
+    Student
+}
+
+public enum MembershipStatus
+{
+    Active,
+    Invited,
+    Disabled
+}

Tiku.Infrastructure/Class1.cs

@@ -1,6 +0,0 @@
-namespace Tiku.Infrastructure;
-
-public class Class1
-{
-
-}

Tiku.Infrastructure/DependencyInjection.cs

@@ -0,0 +1,26 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using Npgsql;
+using Tiku.Infrastructure.Persistence;
+
+namespace Tiku.Infrastructure;
+
+public static class DependencyInjection
+{
+    public static IServiceCollection AddInfrastructure(
+        this IServiceCollection services,
+        string connectionString)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(connectionString);
+
+        services.AddSingleton(_ => NpgsqlDataSource.Create(connectionString));
+        services.AddDbContextPool<TikuDbContext>((serviceProvider, options) =>
+        {
+            var dataSource = serviceProvider.GetRequiredService<NpgsqlDataSource>();
+            options.UseNpgsql(dataSource, npgsql =>
+                npgsql.MigrationsAssembly(typeof(TikuDbContext).Assembly.FullName));
+        });
+
+        return services;
+    }
+}

Tiku.Infrastructure/Persistence/Configurations/CatalogConfigurations.cs

@@ -0,0 +1,187 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using Tiku.Domain.Catalog;
+
+namespace Tiku.Infrastructure.Persistence.Configurations;
+
+internal sealed class RegionConfiguration : IEntityTypeConfiguration<Region>
+{
+    public void Configure(EntityTypeBuilder<Region> builder)
+    {
+        builder.ConfigureTenantEntity("regions");
+        builder.ConfigureTimestamps();
+        builder.Property(entity => entity.LegacyId).HasMaxLength(64);
+        builder.Property(entity => entity.Name).HasMaxLength(200);
+        builder.Property(entity => entity.Code).HasMaxLength(50);
+        builder.Property(entity => entity.ShortName).HasMaxLength(100);
+        builder.Property(entity => entity.FullName).HasMaxLength(300);
+        builder.Property(entity => entity.Icon).HasMaxLength(2048);
+        builder.Property(entity => entity.Pinyin).HasMaxLength(255);
+        builder.Property(entity => entity.Config).IsJson("{}");
+        builder.HasIndex(entity => new { entity.TenantId, entity.LegacyId }).IsUnique();
+    }
+}
+
+internal sealed class RegionModuleConfiguration : IEntityTypeConfiguration<RegionModule>
+{
+    public void Configure(EntityTypeBuilder<RegionModule> builder)
+    {
+        builder.ConfigureTenantEntity("region_modules");
+        builder.ConfigureTimestamps();
+        builder.Property(entity => entity.LegacyId).HasMaxLength(64);
+        builder.Property(entity => entity.Name).HasMaxLength(200);
+        builder.Property(entity => entity.Type).HasMaxLength(50);
+        builder.Property(entity => entity.Icon).HasMaxLength(2048);
+        builder.Property(entity => entity.Color).HasMaxLength(50);
+        builder.Property(entity => entity.TextColor).HasMaxLength(50);
+        builder.Property(entity => entity.Route).HasMaxLength(500);
+        builder.HasIndex(entity => new { entity.TenantId, entity.LegacyId }).IsUnique();
+
+        builder.HasOne<Region>()
+            .WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.RegionId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+    }
+}
+
+internal sealed class ModuleNodeConfiguration : IEntityTypeConfiguration<ModuleNode>
+{
+    public void Configure(EntityTypeBuilder<ModuleNode> builder)
+    {
+        builder.ConfigureTenantEntity("module_nodes");
+        builder.ConfigureTimestamps();
+        builder.Property(entity => entity.LegacyId).HasMaxLength(64);
+        builder.Property(entity => entity.LegacyParentId).HasMaxLength(64);
+        builder.Property(entity => entity.LegacyModuleId).HasMaxLength(64);
+        builder.Property(entity => entity.Type).HasSnakeCaseEnum();
+        builder.Property(entity => entity.Name).HasMaxLength(300);
+        builder.Property(entity => entity.Path).HasMaxLength(1000);
+        builder.Property(entity => entity.Metadata).IsJson("{}");
+        builder.HasIndex(entity => new { entity.TenantId, entity.LegacyId }).IsUnique();
+
+        builder.HasOne<Region>()
+            .WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.RegionId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<RegionModule>()
+            .WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.ModuleId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<ModuleNode>()
+            .WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.ParentId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+    }
+}
+
+internal sealed class SchoolConfiguration : IEntityTypeConfiguration<School>
+{
+    public void Configure(EntityTypeBuilder<School> builder)
+    {
+        builder.ConfigureTenantEntity("schools");
+        builder.ConfigureTimestamps();
+        builder.Property(entity => entity.LegacyId).HasMaxLength(64);
+        builder.Property(entity => entity.Name).HasMaxLength(300);
+        builder.Property(entity => entity.ProfessionalExamDate).HasMaxLength(255);
+        builder.Property(entity => entity.Metadata).IsJson("{}");
+        builder.HasIndex(entity => new { entity.TenantId, entity.LegacyId }).IsUnique();
+
+        builder.HasOne<Region>()
+            .WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.RegionId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<RegionModule>()
+            .WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.ModuleId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+    }
+}
+
+internal sealed class MajorConfiguration : IEntityTypeConfiguration<Major>
+{
+    public void Configure(EntityTypeBuilder<Major> builder)
+    {
+        builder.ConfigureTenantEntity("majors");
+        builder.ConfigureTimestamps();
+        builder.Property(entity => entity.LegacyId).HasMaxLength(64);
+        builder.Property(entity => entity.Name).HasMaxLength(300);
+        builder.HasIndex(entity => new { entity.TenantId, entity.LegacyId }).IsUnique();
+
+        builder.HasOne<Region>()
+            .WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.RegionId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<School>()
+            .WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.SchoolId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+    }
+}
+
+internal sealed class SubjectConfiguration : IEntityTypeConfiguration<Subject>
+{
+    public void Configure(EntityTypeBuilder<Subject> builder)
+    {
+        builder.ConfigureTenantEntity("subjects");
+        builder.ConfigureTimestamps();
+        builder.Property(entity => entity.LegacyId).HasMaxLength(64);
+        builder.Property(entity => entity.Name).HasMaxLength(300);
+        builder.Property(entity => entity.Type).HasNullableSnakeCaseEnum();
+        builder.Property(entity => entity.MajorLegacyIds).IsJson("[]");
+        builder.Property(entity => entity.Icon).HasMaxLength(2048);
+        builder.Property(entity => entity.Stats).IsJson("{}");
+        builder.HasIndex(entity => new { entity.TenantId, entity.LegacyId }).IsUnique();
+
+        builder.HasOne<Region>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.RegionId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<RegionModule>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.ModuleId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<School>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.SchoolId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Major>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.MajorId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<ModuleNode>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.NodeId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+    }
+
+}
+
+internal sealed class CategoryConfiguration : IEntityTypeConfiguration<Category>
+{
+    public void Configure(EntityTypeBuilder<Category> builder)
+    {
+        builder.ConfigureTenantEntity("categories");
+        builder.ConfigureTimestamps();
+        builder.Property(entity => entity.LegacyId).HasMaxLength(64);
+        builder.Property(entity => entity.Name).HasMaxLength(300);
+        builder.Property(entity => entity.CategoryType).HasNullableSnakeCaseEnum();
+        builder.HasIndex(entity => new { entity.TenantId, entity.LegacyId }).IsUnique();
+
+        builder.HasOne<Subject>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.SubjectId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<ModuleNode>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.NodeId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+    }
+}

Tiku.Infrastructure/Persistence/Configurations/ConfigurationSupport.cs

@@ -0,0 +1,75 @@
+using System.Text.Json;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using Tiku.Domain.Common;
+using Tiku.Domain.Tenancy;
+
+namespace Tiku.Infrastructure.Persistence.Configurations;
+
+internal static class ConfigurationSupport
+{
+    public static void ConfigureEntity<TEntity>(
+        this EntityTypeBuilder<TEntity> builder,
+        string tableName)
+        where TEntity : Entity
+    {
+        builder.ToTable(tableName);
+        builder.HasKey(entity => entity.Id);
+        builder.Property(entity => entity.Id).HasDefaultValueSql("gen_random_uuid()");
+    }
+
+    public static void ConfigureTenantEntity<TEntity>(
+        this EntityTypeBuilder<TEntity> builder,
+        string tableName)
+        where TEntity : TenantEntity
+    {
+        builder.ConfigureEntity(tableName);
+        builder.HasAlternateKey(entity => new { entity.TenantId, entity.Id });
+        builder.HasOne<Tenant>()
+            .WithMany()
+            .HasForeignKey(entity => entity.TenantId)
+            .OnDelete(DeleteBehavior.Cascade);
+    }
+
+    public static void ConfigureTimestamps<TEntity>(this EntityTypeBuilder<TEntity> builder)
+        where TEntity : class, IHasTimestamps
+    {
+        builder.Property(entity => entity.CreatedAt).HasDefaultValueSql("now()");
+        builder.Property(entity => entity.UpdatedAt).HasDefaultValueSql("now()");
+    }
+
+    public static PropertyBuilder<JsonElement> IsJson(
+        this PropertyBuilder<JsonElement> property,
+        string defaultJson)
+    {
+        return property
+            .HasColumnType("jsonb")
+            .HasDefaultValueSql($"'{defaultJson}'::jsonb");
+    }
+
+    public static PropertyBuilder<TEnum> HasSnakeCaseEnum<TEnum>(
+        this PropertyBuilder<TEnum> property,
+        int maxLength = 32)
+        where TEnum : struct, Enum
+    {
+        return property
+            .HasConversion(new SnakeCaseEnumConverter<TEnum>())
+            .HasMaxLength(maxLength);
+    }
+
+    public static PropertyBuilder<TEnum?> HasNullableSnakeCaseEnum<TEnum>(
+        this PropertyBuilder<TEnum?> property,
+        int maxLength = 32)
+        where TEnum : struct, Enum
+    {
+        return property
+            .HasConversion(
+                value => value.HasValue
+                    ? ModelBuilderExtensions.ToSnakeCase(value.Value.ToString())
+                    : null,
+                value => string.IsNullOrWhiteSpace(value)
+                    ? null
+                    : Enum.Parse<TEnum>(value.Replace("_", string.Empty), true))
+            .HasMaxLength(maxLength);
+    }
+}

Tiku.Infrastructure/Persistence/Configurations/IdentityConfigurations.cs

@@ -0,0 +1,90 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using Tiku.Domain.Catalog;
+using Tiku.Domain.Identity;
+
+namespace Tiku.Infrastructure.Persistence.Configurations;
+
+internal sealed class UserConfiguration : IEntityTypeConfiguration<User>
+{
+    public void Configure(EntityTypeBuilder<User> builder)
+    {
+        builder.ConfigureEntity("users");
+        builder.ConfigureTimestamps();
+
+        builder.Property(entity => entity.LegacyId).HasMaxLength(64);
+        builder.Property(entity => entity.Username).HasMaxLength(100);
+        builder.Property(entity => entity.Email).HasColumnType("citext").HasMaxLength(320);
+        builder.Property(entity => entity.Phone).HasMaxLength(32);
+        builder.Property(entity => entity.Name).HasMaxLength(200);
+        builder.Property(entity => entity.AvatarUrl).HasMaxLength(2048);
+        builder.Property(entity => entity.PrimaryRole).HasMaxLength(50);
+        builder.Property(entity => entity.LegacyPasswordHash).HasMaxLength(512);
+        builder.Property(entity => entity.RawProfile).IsJson("{}");
+
+        builder.HasIndex(entity => entity.LegacyId).IsUnique();
+        builder.HasIndex(entity => entity.Username).IsUnique();
+        builder.HasIndex(entity => entity.Email).IsUnique();
+        builder.HasIndex(entity => entity.Phone).IsUnique();
+    }
+}
+
+internal sealed class UserIdentityConfiguration : IEntityTypeConfiguration<UserIdentity>
+{
+    public void Configure(EntityTypeBuilder<UserIdentity> builder)
+    {
+        builder.ConfigureEntity("user_identities");
+        builder.ConfigureTimestamps();
+
+        builder.Property(entity => entity.Provider).HasMaxLength(50);
+        builder.Property(entity => entity.ProviderSubject).HasMaxLength(255);
+        builder.Property(entity => entity.UnionId).HasMaxLength(255);
+        builder.Property(entity => entity.OpenId).HasMaxLength(255);
+        builder.Property(entity => entity.Phone).HasMaxLength(32);
+        builder.Property(entity => entity.Email).HasColumnType("citext").HasMaxLength(320);
+        builder.Property(entity => entity.SecretPayload).IsJson("{}");
+
+        builder.HasIndex(entity => new { entity.Provider, entity.ProviderSubject }).IsUnique();
+        builder.HasOne<User>()
+            .WithMany()
+            .HasForeignKey(entity => entity.UserId)
+            .OnDelete(DeleteBehavior.Cascade);
+    }
+}
+
+internal sealed class StudentProfileConfiguration : IEntityTypeConfiguration<StudentProfile>
+{
+    public void Configure(EntityTypeBuilder<StudentProfile> builder)
+    {
+        builder.ConfigureTenantEntity("student_profiles");
+        builder.ConfigureTimestamps();
+
+        builder.Property(entity => entity.LegacyUserId).HasMaxLength(64);
+        builder.Property(entity => entity.Stats).IsJson("{}");
+        builder.Property(entity => entity.Progress).IsJson("{}");
+        builder.Property(entity => entity.ModuleSelections).IsJson("{}");
+        builder.Property(entity => entity.RecentActivities).IsJson("[]");
+
+        builder.HasIndex(entity => new { entity.TenantId, entity.UserId }).IsUnique();
+
+        builder.HasOne<User>()
+            .WithMany()
+            .HasForeignKey(entity => entity.UserId)
+            .OnDelete(DeleteBehavior.Cascade);
+        builder.HasOne<Region>()
+            .WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.RegionId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<School>()
+            .WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.SelectedSchoolId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Major>()
+            .WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.SelectedMajorId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+    }
+}

Tiku.Infrastructure/Persistence/Configurations/LearningConfigurations.cs

@@ -0,0 +1,159 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using Tiku.Domain.Identity;
+using Tiku.Domain.Learning;
+using Tiku.Domain.QuestionBanks;
+using Tiku.Domain.Tenancy;
+
+namespace Tiku.Infrastructure.Persistence.Configurations;
+
+internal sealed class PracticeSessionConfiguration : IEntityTypeConfiguration<PracticeSession>
+{
+    public void Configure(EntityTypeBuilder<PracticeSession> builder)
+    {
+        builder.ConfigureTenantEntity("practice_sessions");
+        builder.HasAlternateKey(entity => new { entity.TenantId, entity.UserId, entity.Id });
+        builder.Property(entity => entity.Mode).HasMaxLength(50);
+        builder.Property(entity => entity.TargetType).HasMaxLength(50);
+        builder.Property(entity => entity.StartedAt).HasDefaultValueSql("now()");
+        builder.Property(entity => entity.Metadata).IsJson("{}");
+        builder.HasIndex(entity => new { entity.TenantId, entity.UserId, entity.StartedAt });
+
+        builder.HasOne<User>().WithMany()
+            .HasForeignKey(entity => entity.UserId)
+            .OnDelete(DeleteBehavior.Cascade);
+    }
+}
+
+internal sealed class AnswerRecordConfiguration : IEntityTypeConfiguration<AnswerRecord>
+{
+    public void Configure(EntityTypeBuilder<AnswerRecord> builder)
+    {
+        builder.ConfigureTenantEntity("answer_records");
+        builder.Property(entity => entity.LegacyId).HasMaxLength(64);
+        builder.Property(entity => entity.LegacyQuestionId).HasMaxLength(64);
+        builder.Property(entity => entity.LegacyCategoryId).HasMaxLength(64);
+        builder.Property(entity => entity.SelectedOptions).IsJson("[]");
+        builder.Property(entity => entity.AnsweredAt).HasDefaultValueSql("now()");
+        builder.Property(entity => entity.CreatedAt).HasDefaultValueSql("now()");
+        builder.HasIndex(entity => new { entity.TenantId, entity.LegacyId }).IsUnique();
+        builder.HasIndex(entity => new { entity.TenantId, entity.QuestionId });
+        builder.HasIndex(entity => new
+        {
+            entity.TenantId,
+            entity.QuestionId,
+            entity.QuestionVersionId
+        });
+        builder.HasIndex(entity => new
+        {
+            entity.TenantId,
+            entity.UserId,
+            entity.PracticeSessionId
+        });
+
+        builder.ToTable(table => table.HasCheckConstraint(
+            "ck_answer_records_version_requires_question",
+            "question_version_id is null or question_id is not null"));
+
+        builder.HasOne<User>().WithMany()
+            .HasForeignKey(entity => entity.UserId)
+            .OnDelete(DeleteBehavior.Cascade);
+        builder.HasOne<Question>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.QuestionId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<QuestionVersion>().WithMany()
+            .HasForeignKey(entity => new
+            {
+                entity.TenantId,
+                entity.QuestionId,
+                entity.QuestionVersionId
+            })
+            .HasPrincipalKey(entity => new
+            {
+                entity.TenantId,
+                entity.QuestionId,
+                entity.Id
+            })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<PracticeSession>().WithMany()
+            .HasForeignKey(entity => new
+            {
+                entity.TenantId,
+                entity.UserId,
+                entity.PracticeSessionId
+            })
+            .HasPrincipalKey(entity => new
+            {
+                entity.TenantId,
+                entity.UserId,
+                entity.Id
+            })
+            .OnDelete(DeleteBehavior.Restrict);
+    }
+}
+
+internal sealed class FavoriteQuestionConfiguration : IEntityTypeConfiguration<FavoriteQuestion>
+{
+    public void Configure(EntityTypeBuilder<FavoriteQuestion> builder)
+    {
+        builder.ToTable("favorite_questions");
+        builder.HasKey(entity => new { entity.TenantId, entity.UserId, entity.QuestionId });
+        builder.Property(entity => entity.Source).HasMaxLength(50);
+        builder.Property(entity => entity.CreatedAt).HasDefaultValueSql("now()");
+
+        builder.HasOne<Tenant>().WithMany()
+            .HasForeignKey(entity => entity.TenantId)
+            .OnDelete(DeleteBehavior.Cascade);
+        builder.HasOne<User>().WithMany()
+            .HasForeignKey(entity => entity.UserId)
+            .OnDelete(DeleteBehavior.Cascade);
+        builder.HasOne<Question>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.QuestionId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Cascade);
+    }
+}
+
+internal sealed class WrongQuestionConfiguration : IEntityTypeConfiguration<WrongQuestion>
+{
+    public void Configure(EntityTypeBuilder<WrongQuestion> builder)
+    {
+        builder.ToTable("wrong_questions");
+        builder.HasKey(entity => new { entity.TenantId, entity.UserId, entity.QuestionId });
+        builder.Property(entity => entity.WrongCount).HasDefaultValue(1);
+        builder.Property(entity => entity.LastWrongAt).HasDefaultValueSql("now()");
+
+        builder.HasOne<Tenant>().WithMany()
+            .HasForeignKey(entity => entity.TenantId)
+            .OnDelete(DeleteBehavior.Cascade);
+        builder.HasOne<User>().WithMany()
+            .HasForeignKey(entity => entity.UserId)
+            .OnDelete(DeleteBehavior.Cascade);
+        builder.HasOne<Question>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.QuestionId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Cascade);
+    }
+}
+
+internal sealed class RecentPracticeConfiguration : IEntityTypeConfiguration<RecentPractice>
+{
+    public void Configure(EntityTypeBuilder<RecentPractice> builder)
+    {
+        builder.ConfigureTenantEntity("recent_practices");
+        builder.ConfigureTimestamps();
+        builder.Property(entity => entity.LegacyId).HasMaxLength(64);
+        builder.Property(entity => entity.PracticeType).HasMaxLength(50);
+        builder.Property(entity => entity.TargetLegacyId).HasMaxLength(64);
+        builder.Property(entity => entity.TargetName).HasMaxLength(300);
+        builder.Property(entity => entity.Color).HasMaxLength(50);
+        builder.Property(entity => entity.Metadata).IsJson("{}");
+        builder.HasIndex(entity => new { entity.TenantId, entity.LegacyId }).IsUnique();
+        builder.HasIndex(entity => new { entity.TenantId, entity.UserId, entity.LastAccessAt });
+
+        builder.HasOne<User>().WithMany()
+            .HasForeignKey(entity => entity.UserId)
+            .OnDelete(DeleteBehavior.Cascade);
+    }
+}

Tiku.Infrastructure/Persistence/Configurations/QuestionConfigurations.cs

@@ -0,0 +1,92 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using Tiku.Domain.Catalog;
+using Tiku.Domain.Identity;
+using Tiku.Domain.QuestionBanks;
+
+namespace Tiku.Infrastructure.Persistence.Configurations;
+
+internal sealed class QuestionBankConfiguration : IEntityTypeConfiguration<QuestionBank>
+{
+    public void Configure(EntityTypeBuilder<QuestionBank> builder)
+    {
+        builder.ConfigureTenantEntity("question_banks");
+        builder.ConfigureTimestamps();
+        builder.Property(entity => entity.Name).HasMaxLength(300);
+        builder.Property(entity => entity.SourceScope).HasSnakeCaseEnum();
+        builder.Property(entity => entity.Status).HasSnakeCaseEnum();
+        builder.Property(entity => entity.Metadata).IsJson("{}");
+
+        builder.HasOne<Region>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.RegionId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+    }
+}
+
+internal sealed class QuestionConfiguration : IEntityTypeConfiguration<Question>
+{
+    public void Configure(EntityTypeBuilder<Question> builder)
+    {
+        builder.ConfigureTenantEntity("questions");
+        builder.ConfigureTimestamps();
+        builder.Property(entity => entity.LegacyId).HasMaxLength(64);
+        builder.Property(entity => entity.LegacySubjectId).HasMaxLength(64);
+        builder.Property(entity => entity.LegacyCategoryId).HasMaxLength(64);
+        builder.Property(entity => entity.LegacyNodeId).HasMaxLength(64);
+        builder.Property(entity => entity.Type).HasMaxLength(50);
+        builder.Property(entity => entity.TypeLabel).HasMaxLength(100);
+        builder.Property(entity => entity.Tags).IsJson("[]");
+        builder.Property(entity => entity.MediaUrl).HasMaxLength(2048);
+        builder.Property(entity => entity.Status).HasSnakeCaseEnum();
+        builder.HasIndex(entity => new { entity.TenantId, entity.LegacyId }).IsUnique();
+
+        builder.HasOne<QuestionBank>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.QuestionBankId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Subject>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.SubjectId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<Category>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.CategoryId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne<ModuleNode>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.NodeId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+
+        builder.HasOne<QuestionVersion>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.Id, entity.CurrentVersionId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.QuestionId, entity.Id })
+            .OnDelete(DeleteBehavior.Restrict);
+    }
+}
+
+internal sealed class QuestionVersionConfiguration : IEntityTypeConfiguration<QuestionVersion>
+{
+    public void Configure(EntityTypeBuilder<QuestionVersion> builder)
+    {
+        builder.ConfigureEntity("question_versions");
+        builder.HasAlternateKey(entity => new { entity.TenantId, entity.Id });
+        builder.HasAlternateKey(entity => new { entity.TenantId, entity.QuestionId, entity.Id });
+
+        builder.Property(entity => entity.Options).IsJson("[]");
+        builder.Property(entity => entity.CorrectOptionIndices).IsJson("[]");
+        builder.Property(entity => entity.SubQuestions).IsJson("[]");
+        builder.Property(entity => entity.CodeLang).HasMaxLength(50);
+        builder.Property(entity => entity.SourceHash).HasMaxLength(128);
+        builder.Property(entity => entity.CreatedAt).HasDefaultValueSql("now()");
+
+        builder.HasIndex(entity => new { entity.QuestionId, entity.VersionNo }).IsUnique();
+        builder.HasOne<Question>().WithMany()
+            .HasForeignKey(entity => new { entity.TenantId, entity.QuestionId })
+            .HasPrincipalKey(entity => new { entity.TenantId, entity.Id })
+            .OnDelete(DeleteBehavior.Cascade);
+        builder.HasOne<User>().WithMany()
+            .HasForeignKey(entity => entity.CreatedBy)
+            .OnDelete(DeleteBehavior.SetNull);
+    }
+}

Tiku.Infrastructure/Persistence/Configurations/TenancyConfigurations.cs

@@ -0,0 +1,53 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using Tiku.Domain.Identity;
+using Tiku.Domain.Tenancy;
+
+namespace Tiku.Infrastructure.Persistence.Configurations;
+
+internal sealed class TenantConfiguration : IEntityTypeConfiguration<Tenant>
+{
+    public void Configure(EntityTypeBuilder<Tenant> builder)
+    {
+        builder.ConfigureEntity("tenants");
+        builder.ConfigureTimestamps();
+
+        builder.Property(entity => entity.Slug).HasColumnType("citext").HasMaxLength(100);
+        builder.Property(entity => entity.Name).HasMaxLength(200);
+        builder.Property(entity => entity.LegalName).HasMaxLength(300);
+        builder.Property(entity => entity.Status).HasSnakeCaseEnum();
+        builder.Property(entity => entity.Mode).HasSnakeCaseEnum();
+        builder.Property(entity => entity.BillingStatus).HasSnakeCaseEnum();
+        builder.Property(entity => entity.LegacyId).HasMaxLength(64);
+        builder.Property(entity => entity.Metadata).IsJson("{}");
+
+        builder.HasIndex(entity => entity.Slug).IsUnique();
+        builder.HasIndex(entity => entity.LegacyId).IsUnique();
+
+        builder.HasOne<User>()
+            .WithMany()
+            .HasForeignKey(entity => entity.OwnerUserId)
+            .OnDelete(DeleteBehavior.SetNull);
+    }
+}
+
+internal sealed class TenantMembershipConfiguration : IEntityTypeConfiguration<TenantMembership>
+{
+    public void Configure(EntityTypeBuilder<TenantMembership> builder)
+    {
+        builder.ConfigureTenantEntity("tenant_memberships");
+        builder.ConfigureTimestamps();
+
+        builder.Property(entity => entity.Role).HasSnakeCaseEnum();
+        builder.Property(entity => entity.Status).HasSnakeCaseEnum();
+        builder.Property(entity => entity.Permissions).IsJson("{}");
+        builder.Property(entity => entity.LegacyRole).HasMaxLength(50);
+
+        builder.HasIndex(entity => new { entity.TenantId, entity.UserId, entity.Role }).IsUnique();
+
+        builder.HasOne<User>()
+            .WithMany()
+            .HasForeignKey(entity => entity.UserId)
+            .OnDelete(DeleteBehavior.Cascade);
+    }
+}

Tiku.Infrastructure/Persistence/ModelBuilderExtensions.cs

@@ -0,0 +1,73 @@
+using System.Text;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+
+namespace Tiku.Infrastructure.Persistence;
+
+internal static class ModelBuilderExtensions
+{
+    public static void UseSnakeCaseIdentifiers(this ModelBuilder modelBuilder)
+    {
+        foreach (var entityType in modelBuilder.Model.GetEntityTypes())
+        {
+            foreach (var property in entityType.GetProperties())
+            {
+                property.SetColumnName(ToSnakeCase(property.Name));
+            }
+
+            foreach (var key in entityType.GetKeys())
+            {
+                if (key.GetName() is { } keyName)
+                {
+                    key.SetName(ToSnakeCase(keyName));
+                }
+            }
+
+            foreach (var foreignKey in entityType.GetForeignKeys())
+            {
+                if (foreignKey.GetConstraintName() is { } constraintName)
+                {
+                    foreignKey.SetConstraintName(ToSnakeCase(constraintName));
+                }
+            }
+
+            foreach (var index in entityType.GetIndexes())
+            {
+                if (index.GetDatabaseName() is { } indexName)
+                {
+                    index.SetDatabaseName(ToSnakeCase(indexName));
+                }
+            }
+        }
+    }
+
+    public static string ToSnakeCase(string value)
+    {
+        if (string.IsNullOrWhiteSpace(value))
+        {
+            return value;
+        }
+
+        var builder = new StringBuilder(value.Length + 8);
+        for (var index = 0; index < value.Length; index++)
+        {
+            var character = value[index];
+            if (char.IsUpper(character) && index > 0 &&
+                (char.IsLower(value[index - 1]) ||
+                 index + 1 < value.Length && char.IsLower(value[index + 1])))
+            {
+                builder.Append('_');
+            }
+
+            builder.Append(char.ToLowerInvariant(character));
+        }
+
+        return builder.ToString();
+    }
+}
+
+internal sealed class SnakeCaseEnumConverter<TEnum>() : ValueConverter<TEnum, string>(
+    value => ModelBuilderExtensions.ToSnakeCase(value.ToString()),
+    value => Enum.Parse<TEnum>(value.Replace("_", string.Empty), true))
+    where TEnum : struct, Enum;

Tiku.Infrastructure/Persistence/TikuDbContext.cs

@@ -0,0 +1,72 @@
+using Microsoft.EntityFrameworkCore;
+using Tiku.Domain.Catalog;
+using Tiku.Domain.Common;
+using Tiku.Domain.Identity;
+using Tiku.Domain.Learning;
+using Tiku.Domain.QuestionBanks;
+using Tiku.Domain.Tenancy;
+
+namespace Tiku.Infrastructure.Persistence;
+
+public sealed class TikuDbContext(DbContextOptions<TikuDbContext> options) : DbContext(options)
+{
+    public DbSet<Tenant> Tenants => Set<Tenant>();
+    public DbSet<User> Users => Set<User>();
+    public DbSet<UserIdentity> UserIdentities => Set<UserIdentity>();
+    public DbSet<TenantMembership> TenantMemberships => Set<TenantMembership>();
+    public DbSet<StudentProfile> StudentProfiles => Set<StudentProfile>();
+    public DbSet<Region> Regions => Set<Region>();
+    public DbSet<RegionModule> RegionModules => Set<RegionModule>();
+    public DbSet<ModuleNode> ModuleNodes => Set<ModuleNode>();
+    public DbSet<School> Schools => Set<School>();
+    public DbSet<Major> Majors => Set<Major>();
+    public DbSet<Subject> Subjects => Set<Subject>();
+    public DbSet<Category> Categories => Set<Category>();
+    public DbSet<QuestionBank> QuestionBanks => Set<QuestionBank>();
+    public DbSet<Question> Questions => Set<Question>();
+    public DbSet<QuestionVersion> QuestionVersions => Set<QuestionVersion>();
+    public DbSet<PracticeSession> PracticeSessions => Set<PracticeSession>();
+    public DbSet<AnswerRecord> AnswerRecords => Set<AnswerRecord>();
+    public DbSet<FavoriteQuestion> FavoriteQuestions => Set<FavoriteQuestion>();
+    public DbSet<WrongQuestion> WrongQuestions => Set<WrongQuestion>();
+    public DbSet<RecentPractice> RecentPractices => Set<RecentPractice>();
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder)
+    {
+        modelBuilder.HasPostgresExtension("citext");
+        modelBuilder.ApplyConfigurationsFromAssembly(typeof(TikuDbContext).Assembly);
+        modelBuilder.UseSnakeCaseIdentifiers();
+    }
+
+    public override int SaveChanges(bool acceptAllChangesOnSuccess)
+    {
+        UpdateTimestamps();
+        return base.SaveChanges(acceptAllChangesOnSuccess);
+    }
+
+    public override Task<int> SaveChangesAsync(
+        bool acceptAllChangesOnSuccess,
+        CancellationToken cancellationToken = default)
+    {
+        UpdateTimestamps();
+        return base.SaveChangesAsync(acceptAllChangesOnSuccess, cancellationToken);
+    }
+
+    private void UpdateTimestamps()
+    {
+        var now = DateTimeOffset.UtcNow;
+
+        foreach (var entry in ChangeTracker.Entries<IHasTimestamps>())
+        {
+            if (entry.State == EntityState.Added)
+            {
+                entry.Entity.CreatedAt = now;
+            }
+
+            if (entry.State is EntityState.Added or EntityState.Modified)
+            {
+                entry.Entity.UpdatedAt = now;
+            }
+        }
+    }
+}

Tiku.Infrastructure/Tiku.Infrastructure.csproj

@@ -5,6 +5,14 @@
     <ProjectReference Include="..\Tiku.Domain\Tiku.Domain.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <PackageReference Include="Microsoft.EntityFrameworkCore" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Relational" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" />
+    <PackageReference Include="Npgsql" />
+    <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" />
+  </ItemGroup>
+
   <PropertyGroup>
     <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>

Tiku.IntegrationTests/PersistenceModelTests.cs

@@ -0,0 +1,68 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata;
+using Tiku.Domain.QuestionBanks;
+using Tiku.Infrastructure.Persistence;
+
+namespace Tiku.IntegrationTests;
+
+public sealed class PersistenceModelTests
+{
+    private static readonly DbContextOptions<TikuDbContext> Options =
+        new DbContextOptionsBuilder<TikuDbContext>()
+            .UseNpgsql("Host=localhost;Database=tiku_model_tests;Username=postgres")
+            .Options;
+
+    [Fact]
+    public void Core_model_contains_expected_tables()
+    {
+        using var context = new TikuDbContext(Options);
+
+        var tableNames = context.Model.GetEntityTypes()
+            .Select(entity => entity.GetTableName())
+            .ToHashSet(StringComparer.Ordinal);
+
+        Assert.Equal(20, tableNames.Count);
+        Assert.Contains("tenants", tableNames);
+        Assert.Contains("questions", tableNames);
+        Assert.Contains("question_versions", tableNames);
+        Assert.Contains("answer_records", tableNames);
+    }
+
+    [Theory]
+    [InlineData(nameof(Question.Tags), "'[]'::jsonb")]
+    public void Question_json_properties_are_mapped_to_jsonb(
+        string propertyName,
+        string expectedDefaultValueSql)
+    {
+        using var context = new TikuDbContext(Options);
+
+        var property = context.Model.FindEntityType(typeof(Question))!
+            .FindProperty(propertyName)!;
+
+        Assert.Equal("jsonb", property.GetColumnType());
+        Assert.Equal(expectedDefaultValueSql, property.GetDefaultValueSql());
+        Assert.Equal(typeof(System.Text.Json.JsonElement), property.ClrType);
+    }
+
+    [Fact]
+    public void Question_relations_include_tenant_in_foreign_keys()
+    {
+        using var context = new TikuDbContext(Options);
+
+        var foreignKeys = context.Model.FindEntityType(typeof(Question))!
+            .GetForeignKeys()
+            .Select(foreignKey => foreignKey.Properties
+                .Select(property => property.Name)
+                .ToArray())
+            .ToArray();
+
+        Assert.All(
+            foreignKeys.Where(properties => properties.Length > 1),
+            properties => Assert.Contains("TenantId", properties));
+
+        Assert.Contains(
+            foreignKeys,
+            properties => properties.SequenceEqual(
+                ["TenantId", "Id", "CurrentVersionId"]));
+    }
+}

Tiku.IntegrationTests/UnitTest1.cs

@@ -1,10 +0,0 @@
-namespace Tiku.IntegrationTests;
-
-public class UnitTest1
-{
-    [Fact]
-    public void Test1()
-    {
-
-    }
-}

dotnet-tools.json

@@ -0,0 +1,13 @@
+{
+  "version": 1,
+  "isRoot": true,
+  "tools": {
+    "dotnet-ef": {
+      "version": "10.0.10",
+      "commands": [
+        "dotnet-ef"
+      ],
+      "rollForward": false
+    }
+  }
+}