feat: 商户冻结/解冻功能及字典缓存重构

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/Domain/TakeoutSaaS.Domain/Dictionary/Entities/DictionaryGroup.cs

@@ -40,9 +40,9 @@ public sealed class DictionaryGroup : MultiTenantEntityBase
     public bool IsEnabled { get; set; } = true;
 
     /// <summary>
-    /// 并发控制字段。
+    /// 并发控制字段（映射到 PostgreSQL xmin）。
     /// </summary>
-    public byte[] RowVersion { get; set; } = Array.Empty<byte>();
+    public uint RowVersion { get; set; }
 
     /// <summary>
     /// 字典项集合。