将 6 组商品相关 App Service 接口/实现从 service/ 及 service/impl/
移至 service/product/ 及 service/product/impl/：
- CustomProductInfoService / CustomProductItemService
- ProductTemplateInfoService / SysBillRuleService
- LogCustomProductService / DiyUserService

纯移动+重命名，无逻辑变更。

Co-Authored-By: Claude <noreply@anthropic.com>