🚫 feat(web): add 403 Forbidden page and AdminRoute guard

- Add new Forbidden page at /forbidden (`web/src/pages/Forbidden/index.js`)
  - Use Semi-UI Empty with IllustrationNoAccess (250x250)
  - Update i18n description to: '您无权访问此页面，请联系管理员~'
  - Align visual style with existing 404 page
- Introduce `AdminRoute` in `web/src/helpers/auth.js`
  - Use `UserContext`/localStorage; redirect to `/forbidden` when `!user` or `user.role < 10`
- Protect console/admin routes with `AdminRoute` and register `/forbidden` in `web/src/App.js`
- Update `web/src/i18n/locales/en.json`
  - Add English translation for the new forbidden message
  - Remove legacy "没有权限" entry
- Lint passes; no runtime errors observed

web/src/pages/NotFound/index.js

@@ -25,7 +25,7 @@ import { useTranslation } from 'react-i18next';
 const NotFound = () => {
   const { t } = useTranslation();
   return (
-    <div className="flex justify-center items-center h-screen p-8 mt-[60px]">
+    <div className="flex justify-center items-center h-screen p-8">
       <Empty
         image={<IllustrationNotFound style={{ width: 250, height: 250 }} />}
         darkModeImage={<IllustrationNotFoundDark style={{ width: 250, height: 250 }} />}