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, 33 insertions, 24 deletions

diff --git a/frontend/src/graphql/queries.graphql b/frontend/src/graphql/queries.graphql
index d08140b..0b0e25c 100644
--- a/frontend/src/graphql/queries.graphql
+++ b/frontend/src/graphql/queries.graphql
@@ -5,41 +5,50 @@ query GetFeeds {
 		title
 		fetchedAt
 		isSubscribed
-		articles {
-			id
-			isRead
-		}
+		unreadCount
 	}
 }
 
-query GetUnreadArticles {
-	unreadArticles {
-		id
-		feedId
-		guid
-		title
-		url
-		isRead
-		feed {
+query GetUnreadArticles($feedId: ID, $after: ID, $first: Int) {
+	unreadArticles(feedId: $feedId, after: $after, first: $first) {
+		articles {
 			id
+			feedId
+			guid
 			title
-			isSubscribed
+			url
+			isRead
+			feed {
+				id
+				title
+				isSubscribed
+			}
+		}
+		pageInfo {
+			hasNextPage
+			endCursor
 		}
 	}
 }
 
-query GetReadArticles {
-	readArticles {
-		id
-		feedId
-		guid
-		title
-		url
-		isRead
-		feed {
+query GetReadArticles($feedId: ID, $after: ID, $first: Int) {
+	readArticles(feedId: $feedId, after: $after, first: $first) {
+		articles {
 			id
+			feedId
+			guid
 			title
-			isSubscribed
+			url
+			isRead
+			feed {
+				id
+				title
+				isSubscribed
+			}
+		}
+		pageInfo {
+			hasNextPage
+			endCursor
 		}
 	}
 }