add account, checkout page

lib/features/cart/presentation/pages/cart_page.dart

@@ -443,12 +443,7 @@ class _CartPageState extends ConsumerState<CartPage> {
         child: ElevatedButton(
           onPressed: cartState.isNotEmpty
               ? () {
-                  // TODO: Navigate to checkout page when implemented
-                  ScaffoldMessenger.of(context).showSnackBar(
-                    const SnackBar(
-                      content: Text('Checkout page chưa được triển khai'),
-                    ),
-                  );
+                  context.push(RouteNames.checkout);
                 }
               : null,
           child: const Text(