refactor: 禁止 TenantId=0 并改为系统租户

src/Application/TakeoutSaaS.Application/Dictionary/Services/DictionaryAppService.cs

@@ -327,7 +327,7 @@ public sealed class DictionaryAppService(
         var tenantId = tenantProvider.GetCurrentTenantId();
         if (scope == DictionaryScope.System)
         {
-            EnsurePlatformTenant(tenantId);
+            EnsureSystemTenant(tenantId);
             return 0;
         }
 
@@ -362,9 +362,9 @@ public sealed class DictionaryAppService(
         }
     }
 
-    private void EnsurePlatformTenant(long tenantId)
+    private void EnsureSystemTenant(long tenantId)
     {
-        // 1. (空行后) 系统字典只能在平台租户（TenantId=0）上下文中操作
+        // 1. (空行后) 系统字典只能在系统租户（TenantId=0）上下文中操作
         if (tenantId != 0)
         {
             throw new BusinessException(ErrorCodes.Forbidden, "租户端不允许操作系统字典");