refactor(shop): 修正创建时间字段类型

- 将 ShopCoupon 类中的 createTime 字段类型从 Data 修改为 Date
- 这个修改解决了类型错误，确保了代码的正确性和一致性

src/main/java/com/gxwebsoft/shop/entity/ShopCoupon.java

@@ -85,7 +85,7 @@ public class ShopCoupon implements Serializable {
     private Integer tenantId;
 
     @Schema(description = "创建时间")
-    private Data createTime;
+    private Date createTime;
 
     @Schema(description = "修改时间")
     private Date updateTime;