feat(frontend): 控制台 next-intl 中英双语

接入无 URL 前缀的 zh-CN/en，顶栏与外观设置可切换语言；选择写入 cookie 后刷新生效。

frontend/app/(main)/proxy-routes/detail/hooks/use-route-section-save.ts

@@ -3,6 +3,8 @@
 import { useCallback, useState } from 'react';
 import { toast } from 'sonner';
 
+import { useTranslations } from 'next-intl';
+
 import type {
   ProxyRouteItem,
   ProxyRouteMutationPayload,
@@ -19,6 +21,7 @@ export function useRouteSectionSave(
   onRouteUpdate: (route: ProxyRouteItem) => void,
   onSavingChange?: (saving: boolean) => void,
 ) {
+  const t = useTranslations('proxyRoutes');
   const [saving, setSaving] = useState(false);
 
   const save = useCallback(
@@ -33,13 +36,15 @@ export function useRouteSectionSave(
         onRouteUpdate(updated);
         toast.success(message);
       } catch (error) {
-        toast.error('保存失败', { description: getErrorMessage(error) });
+        toast.error(t('saveFailed'), {
+          description: getErrorMessage(error, t('requestFailed')),
+        });
       } finally {
         setSaving(false);
         onSavingChange?.(false);
       }
     },
-    [onRouteUpdate, onSavingChange, route],
+    [onRouteUpdate, onSavingChange, route, t],
   );
 
   return { saving, save };