feat(pricing): 优化优惠券领取逻辑与并发控制

- 为 CouponInvalidException 添加错误码支持
- 在 countUserCouponClaims 查询中添加 FOR UPDATE 锁
- 新增 incrementClaimedQuantityIfAvailable 方法用于原子性增加已领取数量
- 移除重复的用户优惠券领取检查逻辑
- 调整领取流程步骤编号并优化事务回滚处理
- 增加对优惠券库存耗尽情况的业务异常处理
- 使用

src/main/java/com/ycwl/basic/pricing/mapper/PriceCouponConfigMapper.java

@@ -38,6 +38,14 @@ public interface PriceCouponConfigMapper extends BaseMapper<PriceCouponConfig> {
     @Update("UPDATE price_coupon_config SET used_quantity = used_quantity + 1, " +
             "update_time = NOW() WHERE id = #{couponId} AND used_quantity < total_quantity")
     int incrementUsedQuantity(Long couponId);
+
+    /**
+     * 原子性增加已领取数量（仅对有限库存的优惠券生效）
+     */
+    @Update("UPDATE price_coupon_config SET claimed_quantity = COALESCE(claimed_quantity, 0) + 1, " +
+            "update_time = NOW() WHERE id = #{couponId} AND total_quantity IS NOT NULL AND total_quantity > 0 " +
+            "AND COALESCE(claimed_quantity, 0) < total_quantity")
+    int incrementClaimedQuantityIfAvailable(@Param("couponId") Long couponId);
     
     /**
      * 插入优惠券配置
@@ -133,4 +141,4 @@ public interface PriceCouponConfigMapper extends BaseMapper<PriceCouponConfig> {
             "SUM(used_quantity) as used_quantity " +
             "FROM price_coupon_config WHERE scenic_id = #{scenicId}")
     java.util.Map<String, Object> selectScenicCouponConfigStats(@Param("scenicId") String scenicId);
-}
+}