Add ProtectedRoute component for route guarding based on authentication

src/routes/protectedRoute.tsx

@@ -0,0 +1,10 @@
+import React from "react";
+import { Navigate, Outlet } from "react-router-dom";
+
+const ProtectedRoute: React.FC = () => {
+  const isAuthenticated = !!localStorage.getItem("auth_token");
+
+  return isAuthenticated ? <Outlet /> : <Navigate to="/signin" />;
+};
+
+export default ProtectedRoute;