Add Google OAuth integration, routing, and theme toggle; implement login and protected routes

Frontend/src/components/ProtectedRoute.jsx

@@ -0,0 +1,21 @@
+import { Navigate } from 'react-router-dom';
+import { useAuth } from '../contexts/AuthContext';
+
+const ProtectedRoute = ({ children }) => {
+  const { isAuthenticated, isLoading } = useAuth();
+
+  if (isLoading) {
+    return (
+      <div className="min-h-screen flex items-center justify-center bg-black">
+        <div className="text-center">
+          <div className="inline-block animate-spin rounded-full h-8 w-8 border-b-2 border-white"></div>
+          <p className="mt-4 text-white">Loading...</p>
+        </div>
+      </div>
+    );
+  }
+
+  return isAuthenticated ? children : <Navigate to="/login" replace />;
+};
+
+export default ProtectedRoute;