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, 3 insertions, 4 deletions

diff --git a/frontend/src/components/ArticleItem.tsx b/frontend/src/components/ArticleItem.tsx
index f8fac24..dbdaf44 100644
--- a/frontend/src/components/ArticleItem.tsx
+++ b/frontend/src/components/ArticleItem.tsx
@@ -10,10 +10,9 @@ import {
 	MarkArticleUnreadDocument,
 } from "../graphql/generated/graphql";
 
-type Article = NonNullable<
-	| GetUnreadArticlesQuery["unreadArticles"]
-	| GetReadArticlesQuery["readArticles"]
->[0];
+type Article =
+	| GetUnreadArticlesQuery["unreadArticles"]["articles"][number]
+	| GetReadArticlesQuery["readArticles"]["articles"][number];
 
 interface Props {
 	article: Article;