Refactor app instance to Keycloak SSO

app-instance/frontend/app/(auth)/register/page.tsx

@@ -3,7 +3,7 @@
 import { useEffect } from 'react';
 import { useSearchParams } from 'next/navigation';
 
-import { buildAuthPortalUrl } from '@/lib/auth-portal';
+import { startKeycloakLogin } from '@/lib/keycloak-oidc';
 import { pickAppText } from '@/lib/i18n/core';
 import { useAppI18n } from '@/lib/i18n/provider';
 
@@ -13,13 +13,13 @@ export default function RegisterRedirectPage() {
 
   useEffect(() => {
     const nextPath = searchParams?.get('next') || '/mcp';
-    window.location.replace(buildAuthPortalUrl('/register', nextPath));
+    void startKeycloakLogin(nextPath);
   }, [searchParams]);
 
   return (
     <div className="flex min-h-screen items-center justify-center px-4">
       <div className="text-sm text-muted-foreground">
-        {pickAppText(locale, '正在跳转到注册门户...', 'Redirecting to the sign-up portal...')}
+        {pickAppText(locale, '正在跳转到 Keycloak 登录...', 'Redirecting to Keycloak sign-in...')}
       </div>
     </div>
   );