feat: enforce tenant isolation and shared question bank

Tiku.Application/Tenancy/TenantDirectoryModels.cs

@@ -0,0 +1,22 @@
+using Tiku.Domain.Tenancy;
+
+namespace Tiku.Application.Tenancy;
+
+public sealed record TenantDirectoryEntry(
+    Guid TenantId,
+    string TenantCode,
+    string Name,
+    TenantStatus Status,
+    TenantMode Mode,
+    string? Host);
+
+public interface ITenantDirectory
+{
+    Task<TenantDirectoryEntry?> FindByHostAsync(
+        string host,
+        CancellationToken cancellationToken = default);
+
+    Task<TenantDirectoryEntry?> FindByCodeAsync(
+        string tenantCode,
+        CancellationToken cancellationToken = default);
+}

Tiku.Application/Tenancy/TenantDomainLifecycleModels.cs

@@ -0,0 +1,39 @@
+namespace Tiku.Application.Tenancy;
+
+public sealed class DomainLifecycleOptions
+{
+    public bool Enabled { get; set; } = true;
+    public int PollSeconds { get; set; } = 60;
+    public int BatchSize { get; set; } = 50;
+    public string DnsJsonEndpoint { get; set; } = "https://cloudflare-dns.com/dns-query";
+    public string VerificationRecordPrefix { get; set; } = "_tiku-verification";
+    public string[] AllowedCnameTargets { get; set; } = [];
+    public string? GatewayBaseUrl { get; set; }
+    public string? GatewayApiKey { get; set; }
+}
+
+public sealed record DomainOwnershipResult(bool Verified, bool Configured, string? FailureReason);
+public sealed record DomainGatewayResult(bool TlsReady, bool Configured, string? FailureReason);
+
+public interface IDomainOwnershipVerifier
+{
+    Task<DomainOwnershipResult> VerifyAsync(
+        string host,
+        string verificationToken,
+        CancellationToken cancellationToken = default);
+}
+
+public interface IDomainGatewayProvisioner
+{
+    Task<DomainGatewayResult> EnsureTlsAsync(string host, CancellationToken cancellationToken = default);
+}
+
+public interface ITenantDomainLifecycleService
+{
+    Task<int> ProcessPendingAsync(CancellationToken cancellationToken = default);
+}
+
+public interface ITenantRuntimeCacheInvalidator
+{
+    void Invalidate(Guid tenantId);
+}

Tiku.Application/Tenancy/TenantFrontendConfigModels.cs

@@ -0,0 +1,47 @@
+using System.Text.Json;
+
+namespace Tiku.Application.Tenancy;
+
+public sealed record TenantFrontendConfigDraft(
+    JsonElement Branding,
+    JsonElement Theme,
+    JsonElement Features,
+    JsonElement Navigation,
+    JsonElement HomeModules);
+
+public sealed record TenantFrontendConfigItem(
+    int SchemaVersion,
+    int ConfigVersion,
+    TenantFrontendConfigDraft Published,
+    TenantFrontendConfigDraft Draft,
+    DateTimeOffset? PublishedAt);
+
+public sealed record TenantRuntimeBootstrap(
+    int SchemaVersion,
+    int ConfigVersion,
+    string TenantCode,
+    string TenantName,
+    JsonElement Branding,
+    JsonElement Theme,
+    JsonElement Features,
+    JsonElement Navigation,
+    JsonElement HomeModules);
+
+public interface ITenantFrontendConfigService
+{
+    Task<TenantFrontendConfigItem> GetAsync(Guid tenantId, CancellationToken cancellationToken = default);
+    Task<TenantFrontendConfigItem> SaveDraftAsync(
+        Guid tenantId,
+        TenantFrontendConfigDraft draft,
+        CancellationToken cancellationToken = default);
+    Task<TenantFrontendConfigItem> PublishAsync(
+        Guid tenantId,
+        int expectedVersion,
+        CancellationToken cancellationToken = default);
+    Task<TenantRuntimeBootstrap> GetRuntimeAsync(Guid tenantId, CancellationToken cancellationToken = default);
+}
+
+public sealed class TenantFrontendConfigException(string code, string message) : Exception(message)
+{
+    public string Code { get; } = code;
+}