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/App.tsx

@@ -62,7 +62,9 @@ function App() {
       <div className="flex flex-1 min-h-0">
       <Sidebar />
       <main className="flex-1 min-w-0">
-        {currentView === "feed" && <Feed />}
+        <div className={currentView === "feed" ? "contents" : "hidden"}>
+          <Feed />
+        </div>
         {currentView === "search" && <SearchView />}
         {currentView === "relays" && <RelaysView />}
         {currentView === "settings" && <SettingsView />}

src/components/feed/Feed.tsx

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