feat: add feed sidebar and cursor-based pagination

Add a feed sidebar to /unread and /read pages for filtering articles by
feed, and replace the fixed 100-article limit with cursor-based
pagination using a "Load more" button.

Backend:
- Add PageInfo, ArticleConnection types and pagination args to GraphQL
- Replace GetUnreadArticles/GetReadArticles with parameterized queries
- Add GetFeedUnreadCounts query and composite index
- Add shared pagination helper in resolver

Frontend:
- Add FeedSidebar component with unread count badges
- Add usePaginatedArticles hook for cursor-based fetching
- Update ArticleList with Load more button and single-feed mode
- Use ?feed=<id> query parameter for feed filtering

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/frontend/src/components/index.ts b/frontend/src/components/index.ts
index 06f4c29..c0797b4 100644
--- a/frontend/src/components/index.ts
+++ b/frontend/src/components/index.ts
@@ -1,6 +1,7 @@
 export { AddFeedForm } from "./AddFeedForm";
 export { ArticleList } from "./ArticleList";
 export { FeedList } from "./FeedList";
+export { FeedSidebar } from "./FeedSidebar";
 export { Layout } from "./Layout";
 export { MenuItem } from "./MenuItem";
 export { Navigation } from "./Navigation";