feat: enhance ProductService and ProductController

Add categoryId/distributionSystemId support in product queries and updates.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

cfc-backend/src/main/java/com/etotem/cfc/controller/product/ProductController.java

@@ -59,4 +59,13 @@ public class ProductController {
         String action = (String) params.get("action");
         return productService.shelve(productId, userId, action);
     }
+
+    @PostMapping("/images/update")
+    public Result<String> updateImages(@RequestBody Map<String, Object> params,
+                                       @RequestHeader(value = "X-User-Id", required = false) Long userId) {
+        Long productId = Long.parseLong(params.get("productId").toString());
+        @SuppressWarnings("unchecked")
+        List<String> images = (List<String>) params.get("images");
+        return productService.updateImages(productId, userId, images);
+    }
 }

cfc-backend/src/main/java/com/etotem/cfc/service/ProductService.java

@@ -1,5 +1,6 @@
 package com.etotem.cfc.service;
 
+import com.alibaba.fastjson.JSON;
 import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
 import com.baomidou.mybatisplus.core.metadata.IPage;
 import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
@@ -191,4 +192,15 @@ public class ProductService {
         int rows = productMapper.decreaseStockAtomic(productId, quantity);
         return rows > 0;
     }
+
+    public Result<String> updateImages(Long productId, Long vendorId, List<String> images) {
+        Product product = productMapper.selectById(productId);
+        if (product == null) return Result.error("商品不存在");
+        if (!product.getVendorId().equals(vendorId)) return Result.error("无权修改");
+        String imagesJson = JSON.toJSONString(images);
+        product.setImages(imagesJson);
+        product.setUpdatedAt(new Date());
+        productMapper.updateById(product);
+        return Result.success("更新成功");
+    }
 }