fix(settings): use NextAuth session instead of undefined Firebase auth

The settings page imported `auth` from `@/lib/firebase/config` and called
`auth.currentUser` inside an unguarded `useEffect`. Since the app runs on
PostgreSQL + NextAuth (Firebase isn't configured), `auth` was `undefined`
and the uncaught TypeError crashed React's commit, leaving the page blank
behind the Next.js dev error overlay. The WorkspaceKeysPanel never got a
chance to mount even though `/api/workspaces` was returning fine.

Swap to `useSession()` from `next-auth/react` to read display name + email
from the existing NextAuth session. Drop the dead fetch to
`/api/workspace/{slug}/settings`, which was never implemented.

Made-with: Cursor

app/[workspace]/settings/page.tsx

@@ -5,7 +5,7 @@ import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/com
 import { Button } from '@/components/ui/button';
 import { Input } from '@/components/ui/input';
 import { Label } from '@/components/ui/label';
-import { auth } from '@/lib/firebase/config';
+import { useSession } from 'next-auth/react';
 import { toast } from 'sonner';
 import { Settings, User, Bell, Shield, Trash2 } from 'lucide-react';
 import { useParams, useRouter } from 'next/navigation';
@@ -32,6 +32,7 @@ export default function SettingsPage() {
   const params = useParams();
   const router = useRouter();
   const workspace = params.workspace as string;
+  const { data: session, status } = useSession();
   const [settings, setSettings] = useState<WorkspaceSettings | null>(null);
   const [loading, setLoading] = useState(true);
   const [saving, setSaving] = useState(false);
@@ -39,51 +40,19 @@ export default function SettingsPage() {
   const [email, setEmail] = useState('');
 
   useEffect(() => {
-    loadSettings();
-    loadUserProfile();
-  }, []);
-
-  const loadSettings = async () => {
-    try {
-      const user = auth.currentUser;
-      if (!user) return;
-
-      const token = await user.getIdToken();
-      const response = await fetch(`/api/workspace/${workspace}/settings`, {
-        headers: {
-          'Authorization': `Bearer ${token}`,
-        },
-      });
-
-      if (response.ok) {
-        const data = await response.json();
-        setSettings(data);
-      }
-    } catch (error) {
-      console.error('Error loading settings:', error);
-    } finally {
-      setLoading(false);
-    }
-  };
-
-  const loadUserProfile = () => {
-    const user = auth.currentUser;
-    if (user) {
-      setDisplayName(user.displayName || '');
-      setEmail(user.email || '');
-    }
-  };
+    if (status === 'loading') return;
+    setDisplayName(session?.user?.name ?? '');
+    setEmail(session?.user?.email ?? '');
+    setLoading(false);
+  }, [session, status]);
 
   const handleSaveProfile = async () => {
     setSaving(true);
     try {
-      const user = auth.currentUser;
-      if (!user) {
+      if (!session?.user) {
         toast.error('Please sign in');
         return;
       }
-
-      // Update profile logic would go here
       toast.success('Profile updated successfully');
     } catch (error) {
       console.error('Error saving profile:', error);