refactor: 重构产品相关Mapper

- 空值处理与类型控制：为相关关系型字段的数据处理添加空值处理与类型控制
- 调整目录结构：将文件目录按照实际查询划分为Product和ProductList两个文件

server/services/cms/productService.ts

@@ -1,7 +1,5 @@
-import {
-  toProductView,
-  toProductListView,
-} from '~~/server/mappers/productMapper';
+import { toProductView } from '~~/server/mappers/productMapper';
+import { toProductListView } from '~~/server/mappers/productListMapper';
 
 export const productService = {
   async getProductList(locale: string) {