feat: enforce tenant isolation and shared question bank

Tiku.Api/Contracts/TenantFrontendConfigDtos.cs

@@ -0,0 +1,28 @@
+using System.ComponentModel.DataAnnotations;
+using System.Text.Json;
+using Tiku.Application.Tenancy;
+using Tiku.Domain.Common;
+
+namespace Tiku.Api.Contracts;
+
+public sealed class SaveTenantFrontendConfigDraftDto
+{
+    public JsonElement Branding { get; set; } = JsonDefaults.Object();
+    public JsonElement Theme { get; set; } = JsonDefaults.Object();
+    public JsonElement Features { get; set; } = JsonDefaults.Object();
+    public JsonElement Navigation { get; set; } = JsonDefaults.Array();
+    public JsonElement HomeModules { get; set; } = JsonDefaults.Array();
+
+    public TenantFrontendConfigDraft ToDraft() => new(
+        Branding,
+        Theme,
+        Features,
+        Navigation,
+        HomeModules);
+}
+
+public sealed class PublishTenantFrontendConfigDto
+{
+    [Range(1, int.MaxValue)]
+    public int ExpectedVersion { get; set; }
+}