feat(pay): 接入微信支付V3原路退款（按支付渠道分流 + 幂等 + 退款回调）

- 新增微信退款客户端 createRefund/queryRefundByOutRefundNo（/v3/refund/domestic/refunds）

- 新增退款桥接模块与 payment_refunds 幂等退款记录表

- 订单退款按渠道分流：微信支付原路退回微信；余额支付退回钱包余额；微信退款失败(502)不回退余额，防重复退款

- 覆盖拒单/买家取消/仲裁全额与部分/超时自动退款；新增 /api/pay/wechat/refund-notify 回调

- 后台新增退款回调地址配置；文档补充退款验收说明

- 新增回归护栏 wechat-refund.spec.ts（77 套件/605 用例全绿）

server/tests/wechat-refund.spec.ts

@@ -0,0 +1,42 @@
+// 已读取AGENTS.md
+import * as fs from 'fs';
+import * as path from 'path';
+
+/**
+ * 第六十一批回归闸门：微信原路退款接入（按支付渠道分流 + 幂等）
+ */
+describe('第六十一批微信原路退款闸门', () => {
+  const rootDir = path.resolve(__dirname, '../../');
+  const payV3 = fs.readFileSync(path.join(rootDir, 'server/src/core/pay/wechat-pay-v3.ts'), 'utf-8');
+  const bridge = fs.readFileSync(path.join(rootDir, 'server/src/core/pay/refund-bridge.ts'), 'utf-8');
+  const repoCode = fs.readFileSync(path.join(rootDir, 'server/src/db/repository.ts'), 'utf-8');
+  const indexCode = fs.readFileSync(path.join(rootDir, 'server/src/index.ts'), 'utf-8');
+  const mysqlCode = fs.readFileSync(path.join(rootDir, 'server/src/db/mysql.ts'), 'utf-8');
+
+  it('支付客户端具备退款与退款查单能力', () => {
+    expect(payV3).toContain('export async function createRefund(');
+    expect(payV3).toContain("'/v3/refund/domestic/refunds'");
+    expect(payV3).toContain('export async function queryRefundByOutRefundNo(');
+  });
+
+  it('退款桥接模块可注入执行器', () => {
+    expect(bridge).toContain('export function setWeChatRefundFn(');
+    expect(bridge).toContain('export async function tryRefundToWeChat(');
+  });
+
+  it('仓储层按支付渠道分流退款并支持幂等记录', () => {
+    expect(repoCode).toContain('private async refundOrderPayment(');
+    expect(repoCode).toContain('private async orderPaidViaWechat(');
+    expect(repoCode).toContain('async getRefundByOutRefundNo(');
+    expect(repoCode).toContain('async upsertRefundRecord(');
+    // 四个退款入口均使用统一分流
+    const count = (repoCode.match(/this\.refundOrderPayment\(/g) || []).length;
+    expect(count).toBeGreaterThanOrEqual(5);
+    expect(mysqlCode).toContain('CREATE TABLE IF NOT EXISTS payment_refunds');
+  });
+
+  it('后端注册退款执行器并提供退款回调', () => {
+    expect(indexCode).toContain('setWeChatRefundFn(async');
+    expect(indexCode).toContain("app.post('/api/pay/wechat/refund-notify'");
+  });
+});