chore: 注册 ActivitiesDetail 页面

- 在 app.config.js 中注册新页面
- 页面路径：pages/ActivitiesDetail/index

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

@@ -31,6 +31,7 @@ export default {
     'pages/EditFamily/index',
     'pages/AlbumList/index',
     'pages/ActivitiesCover/index',
+    'pages/ActivitiesDetail/index',
     'pages/PointsList/index',
     'pages/UploadMedia/index',
     'pages/FamilyRank/index',