fix: add missing isMobile definition in Dashboard

apps/admin/src/pages/Dashboard/index.tsx

@@ -50,6 +50,7 @@ interface ApiResponse<T> { data: T }
 
 const DashboardPage: React.FC = () => {
   const screens = Grid.useBreakpoint();
+  const isMobile = !screens.sm;
   const [stats, setStats] = useState<DashboardStats | null>(null);
   const [roomRanking, setRoomRanking] = useState<Array<{ roomNumber: string; total: string }>>([]);
   const [loading, setLoading] = useState(true);