refactor: 将 Permission 和 MenuDefinition 改为系统级实体

- Permission 和 MenuDefinition 改为继承 AuditableEntityBase（移除 TenantId）
- 添加 PortalType 枚举区分平台端/租户端
- Repository 使用 IgnoreQueryFilters() 查询系统级数据
- 更新所有相关 Handler 和 DTO，移除 TenantId 引用
- 与 AdminApi 保持一致的设计

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

src/Application/TakeoutSaaS.Application/Identity/Handlers/MenuMapper.cs

@@ -1,6 +1,7 @@
 using System.Text.Json;
 using TakeoutSaaS.Application.Identity.Contracts;
 using TakeoutSaaS.Domain.Identity.Entities;
+using TakeoutSaaS.Domain.Identity.Enums;
 
 namespace TakeoutSaaS.Application.Identity.Handlers;
 
@@ -79,23 +80,22 @@ internal static class MenuMapper
     /// 构建或更新菜单实体并返回 DTO。
     /// </summary>
     /// <param name="existing">已存在的菜单实体。</param>
-    /// <param name="tenantId">租户 ID。</param>
-    /// <param name="name">菜单名称。</param>
+    /// <param name="portal">门户类型。</param>
     /// <param name="payload">菜单 DTO 载荷。</param>
     /// <returns>菜单定义 DTO。</returns>
-    public static MenuDefinitionDto FromCommand(MenuDefinition? existing, long tenantId, string name, MenuDefinitionDto payload)
+    public static MenuDefinitionDto FromCommand(MenuDefinition? existing, PortalType portal, MenuDefinitionDto payload)
     {
         // 1. 构造实体
         var entity = existing ?? new MenuDefinition
         {
-            TenantId = tenantId,
+            Portal = portal,
             CreatedAt = DateTime.UtcNow
         };
 
-        // // 填充字段
+        // 2. 填充字段
         FillEntity(entity, payload);
 
-        // 2. 返回 DTO 映射
+        // 3. 返回 DTO 映射
         return ToDto(entity);
     }