- Extract cancelOrderCore() shared by user cancel, admin cancel, and timeout expire
- Query payment platform before cancelling: if already paid, run confirmPayment
- Simplify timeout.ts to delegate to cancelOrderCore
- Cancel API returns already_paid outcome for frontend handling
- Show "订单已支付，无法取消" prompt with back button when cancel is blocked
When cancel API returns error (order already PAID/COMPLETED), immediately
re-poll the order status instead of silently doing nothing. Also check
terminal status before attempting cancel to avoid unnecessary API call.
- Replace zpay with easy-pay payment provider (new lib/easy-pay/ module)
- Add order history page for users (pay/orders)
- Add GET /api/orders/my endpoint to list user's own orders
- Add GET /api/users/[id] endpoint for sub2api user lookup
- Add order status tracking module (lib/order/status.ts)
- Update config to support easy-pay credentials (merchant ID, key, gateway)
- Update PaymentForm and PaymentQRCode components for easy-pay flow
- Update pay page and admin page with new order management UI
- Update order service to support easy-pay, cancellation, and refund
