feat: migrate payment provider to easy-pay, add order history and refund support

- 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

src/instrumentation.ts

@@ -0,0 +1,6 @@
+export async function register() {
+  if (process.env.NEXT_RUNTIME === 'nodejs') {
+    const { startTimeoutScheduler } = await import('@/lib/order/timeout');
+    startTimeoutScheduler();
+  }
+}