feat(mapper): 添加 MemberCouponMapper 接口

添加会员优惠券的 Mapper 接口，继承自 BaseMapper，用于处理会员优惠券相关的数据操作。

src/main/java/com/xynet/marketing/mapper/MemberCouponMapper.java

@@ -0,0 +1,13 @@
+package com.xynet.marketing.mapper;
+
+import com.baomidou.mybatisplus.core.mapper.BaseMapper;
+import com.xynet.marketing.entity.MemberCoupon;
+
+/**
+ * 会员优惠券-Mapper
+ *
+ * @author hechunping
+ * @date 2025/02/10
+ */
+public interface MemberCouponMapper extends BaseMapper<MemberCoupon> {
+}