Preserve feed scroll position across navigation

Keep Feed component mounted (hidden via CSS) instead of unmounting
when navigating to threads/profiles/etc. Back button now returns to
the exact scroll position in the feed.

src/components/feed/Feed.tsx

@@ -24,6 +24,7 @@ export function Feed() {
     connect().then(() => loadFeed());
   }, []);
 
+
   useEffect(() => {
     if (tab === "following" && loggedIn && follows.length > 0) {
       loadFollowFeed();