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/queue/components/QueueTabBar.tsx

@@ -0,0 +1,41 @@
+import { Info, ListMusic, MicVocal } from 'lucide-react';
+import type { TFunction } from 'i18next';
+
+type LyricsTab = 'queue' | 'lyrics' | 'info';
+
+interface Props {
+  activeTab: LyricsTab;
+  setTab: (tab: LyricsTab) => void;
+  t: TFunction;
+}
+
+export function QueueTabBar({ activeTab, setTab, t }: Props) {
+  return (
+    <div className="queue-tab-bar">
+      <button
+        className={`queue-tab-btn${activeTab === 'queue' ? ' active' : ''}`}
+        onClick={() => setTab('queue')}
+        aria-label={t('queue.title')}
+      >
+        <ListMusic size={14} />
+        {t('queue.title')}
+      </button>
+      <button
+        className={`queue-tab-btn${activeTab === 'lyrics' ? ' active' : ''}`}
+        onClick={() => setTab('lyrics')}
+        aria-label={t('player.lyrics')}
+      >
+        <MicVocal size={14} />
+        {t('player.lyrics')}
+      </button>
+      <button
+        className={`queue-tab-btn${activeTab === 'info' ? ' active' : ''}`}
+        onClick={() => setTab('info')}
+        aria-label={t('nowPlayingInfo.tab')}
+      >
+        <Info size={14} />
+        {t('nowPlayingInfo.tab')}
+      </button>
+    </div>
+  );
+}