fix: resolve Google login hydration mismatch and dynamic env load

frontend/src/app/auth/login/LoginForm.tsx

@@ -14,6 +14,7 @@ import { useI18n } from '@/lib/i18n';
 import { apiClient } from '@/lib/apiClient';
 import { useLogin } from './useLogin';
 import type { GoogleAuthResponse } from './types';
+import { useGoogleConfig } from '@/providers/ClientGoogleProvider';
 
 export function LoginForm() {
   const [email, setEmail] = useState('');
@@ -28,7 +29,7 @@ export function LoginForm() {
   const searchParams = useSearchParams();
   const redirect = searchParams.get('redirect') || '/dashboard';
 
-  const googleClientId = process.env.NEXT_PUBLIC_GOOGLE_CLIENT_ID || '';
+  const { clientId: googleClientId, enabled: googleEnabled } = useGoogleConfig();
 
   useEffect(() => {
     if (loginMutation.isError && loginMutation.error) {
@@ -97,7 +98,7 @@ export function LoginForm() {
       </CardHeader>
 
       <CardContent className="space-y-6">
-        {googleClientId && (
+        {googleEnabled && googleClientId && (
           <>
             <div className="flex justify-center">
               {googleLoading ? (