fix(portal): 修复微官网在浏览器打开时的跨域与网络解析报错，支持默认名片平滑降级

backend/src/modules/card/service/portal.ts

@@ -88,6 +88,12 @@ export class CardPortalService extends BaseService {
       card = await this.cardInfoEntity.findOne({
         where: { slug: queryKey },
       });
+      if (!card && queryKey.toLowerCase() === 'default') {
+        card = await this.cardInfoEntity.findOne({
+          where: { status: 'published' },
+          order: { id: 'ASC' },
+        });
+      }
     }
 
     // 3. 实体存在性与发布状态检查