fix: resolve TS2503 Cannot find namespace JSX in App.tsx

src/App.tsx

@@ -1,3 +1,4 @@
+import React from 'react';
 import { Routes, Route, Navigate, useLocation } from 'react-router-dom';
 import Layout from './components/Layout';
 import Dashboard from './pages/Dashboard';
@@ -8,7 +9,7 @@ import ClientDetails from './pages/ClientDetails';
 import Login from './pages/Login';
 import { isAuthenticated } from './dataService';
 
-function PrivateRoute({ children }: { children: JSX.Element }) {
+function PrivateRoute({ children }: { children: React.ReactNode }) {
   const location = useLocation();
   if (!isAuthenticated()) {
     return <Navigate to="/login" state={{ from: location }} replace />;