refactor(queue): co-locate QueuePanel UI into features/queue

Extract the queue UI (QueuePanel + queuePanel/* components + useQueue* hooks)
into features/queue/ with a barrel. This is the chosen playback/queue boundary:
queue = the QueuePanel UI that CONSUMES the playback store; queue STATE and the
audio engine stay in store/ (playback-core, moved separately). Verified
one-way: no playback-core file imports the queue UI back (only doc comments
mention it).

Excluded as NOT queue-UI: useIdlePlayQueuePull (AppShell) and
usePlayQueueSyncLedState (ConnectionIndicator) are queue-SYNC orchestration,
not panel UI — left in hooks/ to move with playback.

Pure move. One test fix: QueuePanel.test.tsx reads its subject via a hardcoded
readFileSync('src/components/QueuePanel.tsx') path (architecture-pin grep for
forbidden HTML5 DnD) — repointed to the new location (the move tool can't
rewrite non-import string paths). tsc 0, lint 0/0, suite 319/2353 green.

src/features/fullscreenPlayer/components/FullscreenPlayerStatic.tsx

@@ -13,7 +13,7 @@ import { useArtistFanart } from '@/cover/useArtistFanart';
 import { backdropFromConfig } from '@/cover/artistBackdrop';
 import { useThemeStore } from '@/store/themeStore';
 import { useFsIdleFade } from '@/hooks/useFsIdleFade';
-import { useQueueTrackAt } from '@/hooks/useQueueTracks';
+import { useQueueTrackAt } from '@/features/queue';
 import { WaveformSeek } from '@/features/waveform';
 import { FsQueueModal } from '@/features/fullscreenPlayer/components/FsQueueModal';
 import { FsLyricsApple } from '@/features/fullscreenPlayer/components/FsLyricsApple';