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/lib/order/status.ts

@@ -0,0 +1,66 @@
+export type RechargeStatus =
+  | 'not_paid'
+  | 'paid_pending'
+  | 'recharging'
+  | 'success'
+  | 'failed'
+  | 'closed';
+
+export interface OrderStatusLike {
+  status: string;
+  paidAt?: Date | string | null;
+  completedAt?: Date | string | null;
+}
+
+const CLOSED_STATUSES = new Set([
+  'EXPIRED',
+  'CANCELLED',
+  'REFUNDING',
+  'REFUNDED',
+  'REFUND_FAILED',
+]);
+
+const REFUND_STATUSES = new Set(['REFUNDING', 'REFUNDED', 'REFUND_FAILED']);
+
+function hasDate(value: Date | string | null | undefined): boolean {
+  return Boolean(value);
+}
+
+export function isRefundStatus(status: string): boolean {
+  return REFUND_STATUSES.has(status);
+}
+
+export function isRechargeRetryable(order: OrderStatusLike): boolean {
+  return hasDate(order.paidAt) && order.status === 'FAILED' && !isRefundStatus(order.status);
+}
+
+export function deriveOrderState(order: OrderStatusLike): {
+  paymentSuccess: boolean;
+  rechargeSuccess: boolean;
+  rechargeStatus: RechargeStatus;
+} {
+  const paymentSuccess = hasDate(order.paidAt);
+  const rechargeSuccess = hasDate(order.completedAt) || order.status === 'COMPLETED';
+
+  if (rechargeSuccess) {
+    return { paymentSuccess, rechargeSuccess: true, rechargeStatus: 'success' };
+  }
+
+  if (order.status === 'RECHARGING') {
+    return { paymentSuccess, rechargeSuccess: false, rechargeStatus: 'recharging' };
+  }
+
+  if (order.status === 'FAILED') {
+    return { paymentSuccess, rechargeSuccess: false, rechargeStatus: 'failed' };
+  }
+
+  if (CLOSED_STATUSES.has(order.status)) {
+    return { paymentSuccess, rechargeSuccess: false, rechargeStatus: 'closed' };
+  }
+
+  if (paymentSuccess) {
+    return { paymentSuccess, rechargeSuccess: false, rechargeStatus: 'paid_pending' };
+  }
+
+  return { paymentSuccess: false, rechargeSuccess: false, rechargeStatus: 'not_paid' };
+}