feat(coupon): 优惠券中心（领取）+ 我的券 + 下单核销/回退

- 新表 user_coupons（快照面额/门槛/类目/有效期）+ orders.user_coupon_id
- 仓储：getCouponsWithClaimed/claimCoupon/getUserCoupons/resolveUserCoupon/consumeUserCoupon/releaseUserCouponByOrder
- 接口：POST /api/marketing/coupons/:id/claim（同券仅一次、受总量限制）、GET /api/marketing/my-coupons（自动标记过期）、券中心带 claimed 标识
- 下单：createOrder 支持 userCouponId（校验归属/门槛/类目/有效期，服务端算抵扣，与订单同事务占用）
- 回退：买家取消/大神拒单/超时退款/仲裁退款 均把券退回为 UNUSED
- 小程序：新增 pages/user/coupons（券中心+我的券）、个人中心入口(可用张数)、下单改为选择"我的券"并传 userCouponId
- 回归 94 套件/666 用例全绿；冒烟 9/9（领取/重复领取409/不存在404/下单抵扣100-10=90/取消回退）

server/src/index.ts

@@ -1728,13 +1728,51 @@ app.delete('/api/admin/recharge-tiers/:id', async (req: Request, res: Response)
 app.get('/api/marketing/coupons', async (req: Request, res: Response) => {
   try {
     const category = req.query.category ? String(req.query.category) : undefined;
-    const list = await repo.getCoupons(category);
+    const uid = Number(req.query.userId || req.headers['x-user-id'] || 0) || 0;
+    const list = await repo.getCouponsWithClaimed(uid, category);
     res.json({ code: 20000, data: list });
   } catch (err: any) {
     res.status(500).json({ code: 50000, message: err.message });
   }
 });
 
+// 领取优惠券（同一用户同一券仅可领一次）
+app.post('/api/marketing/coupons/:id/claim', async (req: Request, res: Response) => {
+  try {
+    const couponId = Number(req.params.id);
+    const uid = resolveSecureUserId(
+      req,
+      Number(req.body?.userId || req.query.userId || req.headers['x-user-id'] || 0),
+      '领取优惠券'
+    );
+    const claimed = await repo.claimCoupon(uid, couponId);
+    res.json({ code: 20000, data: claimed, message: '优惠券领取成功' });
+  } catch (err: any) {
+    const statusCode = err.status || 400;
+    const errCode = err.code || 40000;
+    res.status(statusCode).json({ code: errCode, message: err.message });
+  }
+});
+
+// 我的优惠券（status: UNUSED | USED | EXPIRED，缺省返回全部）
+app.get('/api/marketing/my-coupons', async (req: Request, res: Response) => {
+  try {
+    const uid = resolveSecureUserId(
+      req,
+      Number(req.query.userId || req.headers['x-user-id'] || 0),
+      '查看我的优惠券'
+    );
+    const status = req.query.status ? String(req.query.status) : undefined;
+    const list = await repo.getUserCoupons(uid, status);
+    const usable = list.filter((c: any) => c.status === 'UNUSED').length;
+    res.json({ code: 20000, data: { list, usable } });
+  } catch (err: any) {
+    const statusCode = err.status || 400;
+    const errCode = err.code || 40000;
+    res.status(statusCode).json({ code: errCode, message: err.message });
+  }
+});
+
 // 管理后台：获取全部优惠券
 app.get('/api/admin/coupons', async (_req: Request, res: Response) => {
   try {