feat: integrate Stripe payment module with API + UI components

src/modules/payments/index.js

@@ -0,0 +1,13 @@
+/**
+ * Payments Module — public surface.
+ *
+ * Self-contained Stripe Checkout integration. Import from here so the rest of
+ * the app never reaches into the module internals.
+ */
+
+export { default as PaymentsPage } from './pages/PaymentsPage';
+export { default as PaymentSuccess } from './pages/PaymentSuccess';
+export { default as PaymentCancelled } from './pages/PaymentCancelled';
+export { default as DemoCheckout } from './pages/DemoCheckout';
+export { PaymentProvider, usePayments } from './context/PaymentProvider';
+export { stripeConfig } from './config/stripeConfig';