- Added a new endpoint `/stripe/finalize-checkout` to synchronously fulfill a checkout session, addressing the webhook-vs-redirect race condition.
- Updated the `PurchaseSuccessPage` component to handle various states of the checkout process, including loading, completed, pending, and failed states.
- Introduced a new response model `FinalizeCheckoutResponse` to provide immediate feedback on the purchase status.
- Enhanced the Stripe API service to include the new finalize checkout functionality.
