Payment Gateway Integration Integrate secure payment processing with proper error handling and compliance. Stripe Integration (Node.js) Webhook Handling PayPal Integration See references/paypal-integration.md for complete PayPal implementation with: - Order creation and capture - Refund processing - Webhook handling - Frontend SDK integration - Success/cancel callbacks Security Checklist - [ ] Use official SDK only - [ ] Verify webhook signatures - [ ] Never log full card numbers - [ ] Store minimal payment data - [ ] Test in sandbox first - [ ] HTTPS for all payment routes - [ ] Handle all e…