refactor: Step 0.1 — Controller 层子包拆分

- 将 5 个产品相关 Controller 从 controller/ 移至 controller/product/
- 更新包声明从 .controller 为 .controller.product
- HealthController.java 保留在顶层 controller/ 目录

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

custom-server-webapp/src/main/java/com/jomalls/custom/webapp/controller/CustomProductInfoController.java → custom-server-webapp/src/main/java/com/jomalls/custom/webapp/controller/product/CustomProductInfoController.java

-package com.jomalls.custom.webapp.controller;
+package com.jomalls.custom.webapp.controller.product;
 
 import com.baomidou.mybatisplus.core.metadata.IPage;
 import com.jomalls.custom.app.dto.*;

custom-server-webapp/src/main/java/com/jomalls/custom/webapp/controller/CustomProductItemController.java → custom-server-webapp/src/main/java/com/jomalls/custom/webapp/controller/product/CustomProductItemController.java

-package com.jomalls.custom.webapp.controller;
+package com.jomalls.custom.webapp.controller.product;
 
 import com.jomalls.custom.app.constant.Constants;
 import com.jomalls.custom.app.dto.UpdateSalesPriceSnakeDTO;

custom-server-webapp/src/main/java/com/jomalls/custom/webapp/controller/LogCustomProductController.java → custom-server-webapp/src/main/java/com/jomalls/custom/webapp/controller/product/LogCustomProductController.java

-package com.jomalls.custom.webapp.controller;
+package com.jomalls.custom.webapp.controller.product;
 
 import com.jomalls.custom.app.service.LogCustomProductService;
 import com.jomalls.custom.app.vo.LogCustomProductSnakeVO;

custom-server-webapp/src/main/java/com/jomalls/custom/webapp/controller/ProductTemplateInfoController.java → custom-server-webapp/src/main/java/com/jomalls/custom/webapp/controller/product/ProductTemplateInfoController.java

-package com.jomalls.custom.webapp.controller;
+package com.jomalls.custom.webapp.controller.product;
 
 import com.jomalls.custom.app.service.ProductTemplateInfoService;
 import com.jomalls.custom.app.vo.BindDetailVO;

custom-server-webapp/src/main/java/com/jomalls/custom/webapp/controller/SysBillRuleController.java → custom-server-webapp/src/main/java/com/jomalls/custom/webapp/controller/product/SysBillRuleController.java

-package com.jomalls.custom.webapp.controller;
+package com.jomalls.custom.webapp.controller.product;
 
 import com.jomalls.custom.app.service.SysBillRuleService;
 import io.swagger.v3.oas.annotations.Operation;