feat(AlibabaAgent): 添加主图参数传递到SKU插入方法

- 在insertStoreSkus方法中新增$mainImage参数
- 将商品主图传递给SKU数据插入流程
- 为默认SKU设置主图为默认图片字段值

app/services/ThirdParty/AlibabaAgent/ProductService.php

@@ -487,7 +487,7 @@ class ProductService extends AlibabaAgentBaseService
             ]);
 
             // 9. 写入 store_product_attr 和 store_product_attr_value
-            $this->insertStoreSkus($productId, $skuList, $merId, $costPrice);
+            $this->insertStoreSkus($productId, $skuList, $merId, $costPrice,$mainImage);
 
             Log::channel('alibaba')->info("[1688正式入库1] 商品{$importGoods['product_id']}入库成功，product_id={$productId}，mer_id={$merId}");
 
@@ -509,7 +509,7 @@ class ProductService extends AlibabaAgentBaseService
      * @param array $skuList    formatDetailResult 返回的 skuList
      * @param int   $merId
      */
-    protected function insertStoreSkus(int $productId, array $skuList, int $merId, $costPrice): void
+    protected function insertStoreSkus(int $productId, array $skuList, int $merId, $costPrice, $mainImage): void
     {
         if (empty($skuList)) {
             // 单规格：写入默认规格
@@ -525,7 +525,7 @@ class ProductService extends AlibabaAgentBaseService
                 'product_id'  => $productId,
                 'detail'      => json_encode(['规格' => '默认'], JSON_UNESCAPED_UNICODE),
                 'sku'         => '默认',
-                'image'       => '',
+                'image'       => $mainImage,
                 'cost'        => $costPrice,
                 'ot_price'    => $costPrice,
                 'price'       => $costPrice,