Build a Stripe Payment Checkout Page

Create a /checkout page for this app using Stripe in test mode. The page should display the product name, price ($29/month), and a bullet list of 3 key features. Add a "Pay with Stripe" button that calls a serverless function to create a Stripe Checkout Session with the correct price ID, success_url pointing to /thank-you?session_id={CHECKOUT_SESSION_ID}, and cancel_url pointing back to /checkout. Redirect the user to Stripe's hosted checkout page after the session is created. On the /thank-you page, retrieve the session ID from the URL, confirm the payment was successful via the Stripe API, and display a personalized confirmation message with the user's email. Use Stripe test mode keys (starting with sk_test_ and pk_test_) throughout.