feat(i18n): add internationalization support with English and Chinese translations

webapp/src/components/HelpPage.tsx

@@ -1,22 +1,17 @@
+import { Construction } from 'lucide-preact';
+import { t } from '@/lib/i18n';
+
 export default function HelpPage() {
   return (
     <div className="stack">
       <section className="card">
-        <h3>Upstream Sync</h3>
-        <ul>
-          <li>Use fork + scheduled sync workflow.</li>
-          <li>Before merging, compare API routes and auth flow changes.</li>
-          <li>After merging, run migration tests in local dev before deploy.</li>
-        </ul>
-      </section>
-      <section className="card">
-        <h3>Common Errors</h3>
-        <ul>
-          <li>401 Unauthorized: token expired, log in again.</li>
-          <li>403 Account disabled: admin must unban your account.</li>
-          <li>403 Invite invalid: invite expired or revoked.</li>
-          <li>429 Too many requests: wait and retry.</li>
-        </ul>
+        <h3>{t('support_title')}</h3>
+        <div className="empty" style={{ minHeight: 180 }}>
+          <div style={{ textAlign: 'center' }}>
+            <Construction size={34} style={{ color: '#64748b', marginBottom: 8 }} />
+            <div>{t('support_under_construction')}</div>
+          </div>
+        </div>
       </section>
     </div>
   );