fix(mui): restore delete-dialog loading state on Users (parity with original ConfirmModal)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/pages/Users.tsx

@@ -478,6 +478,7 @@ export default function Users() {
         }
         confirmText="Smazat"
         confirmVariant="danger"
+        loading={deleteUser.isPending}
       />
     </Box>
   );