feat: 新增店铺联级查询接口

- 新增 GET /api/admin/shops/cascade 接口，支持按店铺名模糊查询和上级ID过滤
- Store 层新增 ListForCascade（支持数据权限过滤）和 GetParentIDsWithChildren 方法
- Service 层新增 ListCascade，批量判断 has_children 避免 N+1 查询
- 返回格式：[{id, shop_name, has_children}]

💘 Generated with Crush

Assisted-by: Claude Sonnet 4.6 via Crush <crush@charm.land>

internal/service/shop/service.go

@@ -350,6 +350,44 @@ func (s *Service) List(ctx context.Context, opts *store.QueryOptions, filters ma
 	return s.shopStore.List(ctx, opts, filters)
 }
 
+// ListCascade 联级查询店铺，用于新增店铺或其他场景选择上级店铺
+func (s *Service) ListCascade(ctx context.Context, req *dto.ShopCascadeRequest) ([]*dto.ShopCascadeItem, error) {
+	shops, err := s.shopStore.ListForCascade(ctx, req.ShopName, req.ParentID)
+	if err != nil {
+		return nil, errors.Wrap(errors.CodeInternalError, err, "查询店铺失败")
+	}
+
+	if len(shops) == 0 {
+		return []*dto.ShopCascadeItem{}, nil
+	}
+
+	ids := make([]uint, 0, len(shops))
+	for _, shop := range shops {
+		ids = append(ids, shop.ID)
+	}
+
+	childParentIDs, err := s.shopStore.GetParentIDsWithChildren(ctx, ids)
+	if err != nil {
+		return nil, errors.Wrap(errors.CodeInternalError, err, "查询下级店铺失败")
+	}
+
+	hasChildrenSet := make(map[uint]bool, len(childParentIDs))
+	for _, pid := range childParentIDs {
+		hasChildrenSet[pid] = true
+	}
+
+	result := make([]*dto.ShopCascadeItem, 0, len(shops))
+	for _, shop := range shops {
+		result = append(result, &dto.ShopCascadeItem{
+			ID:          shop.ID,
+			ShopName:    shop.ShopName,
+			HasChildren: hasChildrenSet[shop.ID],
+		})
+	}
+
+	return result, nil
+}
+
 func (s *Service) Delete(ctx context.Context, id uint) error {
 	currentUserID := middleware.GetUserIDFromContext(ctx)
 	if currentUserID == 0 {