feat: enforce tenant isolation and shared question bank

Tiku.Api/Contracts/TaxonomyDtos.cs

@@ -0,0 +1,31 @@
+using System.ComponentModel.DataAnnotations;
+using System.Text.Json;
+using Tiku.Application.Catalog;
+using Tiku.Domain.Catalog;
+using Tiku.Domain.Common;
+using Tiku.Domain.Content;
+
+namespace Tiku.Api.Contracts;
+
+public sealed class CreateTaxonomyNodeDto
+{
+    public Guid? ParentId { get; set; }
+    public QuestionSource? ParentSource { get; set; }
+    [Required]
+    public TaxonomyNodeType NodeType { get; set; }
+    [Required, StringLength(100)]
+    public string Code { get; set; } = string.Empty;
+    [Required, StringLength(300)]
+    public string Name { get; set; } = string.Empty;
+    public int SortOrder { get; set; }
+    public JsonElement Metadata { get; set; } = JsonDefaults.Object();
+
+    public CreateTaxonomyNodeCommand ToCommand() => new(
+        ParentId,
+        ParentSource,
+        NodeType,
+        Code,
+        Name,
+        SortOrder,
+        Metadata);
+}