feat(trade): connect WeChat refund API and callback flow

Co-authored-by: Cursor <cursoragent@cursor.com>

server/dukang-api/src/integrations/pay/pay.router.provider.ts

@@ -1,6 +1,6 @@
 import { Injectable } from '@nestjs/common';
 import { loadAppConfig } from '@dukang/shared-types';
-import type { IPayProvider, PayMethod, PayOrderResult } from './pay.interface';
+import type { IPayProvider, PayMethod, PayOrderResult, RefundOrderResult } from './pay.interface';
 import { PayMockProvider } from './pay.mock.provider';
 import { PayWechatProvider } from './pay.wechat.provider';
 
@@ -24,4 +24,12 @@ export class PayRouterProvider implements IPayProvider {
   ): Promise<PayOrderResult> {
     return this.resolve().payOrder(orderId, openId, platform, payMethod);
   }
+
+  refundOrder(
+    orderId: bigint,
+    outRefundNo: string,
+    reason?: string,
+  ): Promise<RefundOrderResult> {
+    return this.resolve().refundOrder(orderId, outRefundNo, reason);
+  }
 }