fix: Use username field instead of display_name in profile

- Updated profile-actions.ts to use username column
- Updated ProfileForm.tsx to use username
- Updated settings page to pass username
- Matches database schema (profiles.username)

src/components/ProfileForm.tsx

@@ -8,12 +8,12 @@ import { updateProfile } from '@/services/profile-actions';
 interface ProfileFormProps {
     initialData: {
         email?: string;
-        display_name?: string | null;
+        username?: string | null;
     };
 }
 
 export default function ProfileForm({ initialData }: ProfileFormProps) {
-    const [displayName, setDisplayName] = useState(initialData.display_name || '');
+    const [username, setUsername] = useState(initialData.username || '');
     const [isPending, startTransition] = useTransition();
     const [status, setStatus] = useState<'idle' | 'success' | 'error'>('idle');
     const [error, setError] = useState<string | null>(null);
@@ -24,7 +24,7 @@ export default function ProfileForm({ initialData }: ProfileFormProps) {
         setError(null);
 
         const formData = new FormData();
-        formData.set('display_name', displayName);
+        formData.set('username', username);
 
         startTransition(async () => {
             const result = await updateProfile(formData);
@@ -66,16 +66,16 @@ export default function ProfileForm({ initialData }: ProfileFormProps) {
                     <p className="mt-1 text-xs text-zinc-500">E-Mail kann nicht geändert werden</p>
                 </div>
 
-                {/* Display Name */}
+                {/* Username */}
                 <div>
                     <label className="block text-sm font-medium text-zinc-400 mb-2">
-                        Anzeigename
+                        Benutzername
                     </label>
                     <input
                         type="text"
-                        value={displayName}
-                        onChange={(e) => setDisplayName(e.target.value)}
-                        placeholder="Dein Name"
+                        value={username}
+                        onChange={(e) => setUsername(e.target.value)}
+                        placeholder="Dein Benutzername"
                         className="w-full px-4 py-3 bg-zinc-800 border border-zinc-700 rounded-xl text-white placeholder-zinc-500 focus:outline-none focus:ring-2 focus:ring-orange-500 focus:border-transparent"
                     />
                 </div>