Rewrite in TS

frontend/src/index.tsx

@@ -0,0 +1,10 @@
+import { createRoot } from 'react-dom/client';
+import App from './App';
+import './index.css';
+
+const container = document.getElementById('root');
+if (!container) {
+  throw new Error('Root element not found');
+}
+const root = createRoot(container);
+root.render(<App />);