Fix users endpoint response format to match frontend expectation

Wrap getPaginatedUsers result in { data: result } to match the project
convention and frontend code that expects response.data.users.

routes/admin.js

@@ -71,7 +71,7 @@ router.get('/users', async (req, res) => {
       order
     });
 
-    res.json(result);
+    res.json({ data: result });
   } catch (error) {
     console.error('Error fetching users:', error);
     res.status(500).json({ error: 'Failed to fetch users' });