feat: 新增后台复制店铺商品目录接口

支持按用户ID复制商品类型、专区与商品，OSS图片独立拷贝，并提供覆盖/补充两种模式。

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/view.py

@@ -63,6 +63,7 @@ from .views.system import (
 from .views.shops import (
     ShopListView, ShopModifyView, ShopPublicTypeAndAuditView, ShopListForProductView,
     ShopProductTypeMappingView, ShopProductModifyView, ProductListView, ProductModifyView,
+    ShopCopyCatalogView,
 )
 from .views.penalties import (
     FaKuanTongJiView, FaKuanLieBiaoView, FaKuanChuLiView, FaKuanPingTaiShenHeView,
@@ -117,6 +118,7 @@ __all__ = [
     # shops
     'ShopListView', 'ShopModifyView', 'ShopPublicTypeAndAuditView', 'ShopListForProductView',
     'ShopProductTypeMappingView', 'ShopProductModifyView', 'ProductListView', 'ProductModifyView',
+    'ShopCopyCatalogView',
     # penalties
     'FaKuanTongJiView', 'FaKuanLieBiaoView', 'FaKuanChuLiView', 'FaKuanPingTaiShenHeView',
     'FaKuanChuangJianView', 'FineApplyView', 'PunishDashouView',