Refactor: Centralized Supabase Auth and implemented Auth Guards to prevent 401 errors

src/components/SessionList.tsx

@@ -8,6 +8,7 @@ import AvatarStack from './AvatarStack';
 import { deleteSession } from '@/services/delete-session';
 import { useI18n } from '@/i18n/I18nContext';
 import { useSession } from '@/context/SessionContext';
+import { useAuth } from '@/context/AuthContext';
 
 interface Session {
     id: string;
@@ -34,10 +35,13 @@ export default function SessionList() {
     });
     const [newName, setNewName] = useState('');
     const { activeSession, setActiveSession } = useSession();
+    const { user, isLoading: isAuthLoading } = useAuth();
 
     useEffect(() => {
-        fetchSessions();
-    }, []);
+        if (!isAuthLoading && user) {
+            fetchSessions();
+        }
+    }, [user, isAuthLoading]);
 
     const fetchSessions = async () => {
         const { data, error } = await supabase