refactor(zone): remove legacy route domain storage

第二阶段清理：删除 of_managed_domains 与 of_proxy_routes 冗余域名/证书列，
移除 ManagedDomain 模型与 API、路由侧 legacy 字段维护，以及前端 WebsiteService。
ImportLegacy 在旧列/旧表缺失时跳过对应源，保持幂等。

frontend/app/(main)/websites/components/certificate-editor-dialog.tsx

@@ -62,8 +62,7 @@ export function CertificateEditorDialog({
     onSuccess: async (certificate) => {
       await Promise.all([
         queryClient.invalidateQueries({queryKey: certificatesQueryKey}),
-        queryClient.invalidateQueries({queryKey: ['openflare', 'managed-domains']}),
-      ]);
+              ]);
       onSaved?.(certificate);
       handleClose();
     },

frontend/app/(main)/websites/components/certificate-import-dialog.tsx

@@ -58,8 +58,7 @@ export function CertificateImportDialog({
   const invalidateQueries = async () => {
     await Promise.all([
       queryClient.invalidateQueries({queryKey: certificatesQueryKey}),
-      queryClient.invalidateQueries({queryKey: ['openflare', 'managed-domains']}),
-    ]);
+          ]);
   };
 
   const resetFileForm = () => {