feat(player): Now Playing overlay + synced lyrics panel (A1/A11, §6.7)

Full-screen overlay expanded from the persistent player: big artwork or a
Lyrics tab. Synced (LRC) lyrics highlight the active line by playback position,
auto-scroll, and seek on tap; plain text is the fallback; missing lyrics offers
a re-fetch. Adds lyrics endpoint + LRC parser + isNowPlayingOpen player state.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/components/layout/AppShell.tsx

@@ -2,6 +2,7 @@ import { Outlet } from 'react-router';
 import { Suspense } from 'react';
 import { Sidebar } from './Sidebar';
 import { PersistentPlayer } from '../player/PersistentPlayer';
+import { NowPlaying } from '../player/NowPlaying';
 import { QueuePanel } from '../player/QueuePanel';
 import { TrackInfoDrawer } from '../track/TrackInfoDrawer';
 import { AddToPlaylistDialog } from '../track/AddToPlaylistDialog';
@@ -37,6 +38,7 @@ export function AppShell() {
       </div>
       <AddToPlaylistDialog />
       <PersistentPlayer />
+      <NowPlaying />
     </div>
   );
 }