feat(queue): unified persistent queue list with playing indicator

Show all queue entries (played and upcoming) in one list instead of
splitting into a "Now playing" card + "Next up" tail, so previously
played tracks don't disappear and reappear when navigating back/forward.
The current track is outlined and shows a reusable "hopping bars"
PlayingIndicator (modern-sk style equalizer animation) for future reuse
across track lists.

src/components/common/PlayingIndicator.tsx

@@ -0,0 +1,22 @@
+/*
+ * "Hopping bars" equalizer indicator (YTM-style) shown next to the currently
+ * playing track. `animate` controls whether the bars bounce (playback active)
+ * or sit frozen at full height (paused). Reusable across track lists.
+ */
+interface Props {
+  animate?: boolean;
+  className?: string;
+}
+
+export function PlayingIndicator({ animate = true, className }: Props) {
+  return (
+    <span
+      className={`playing-bars${animate ? '' : ' paused'}${className ? ` ${className}` : ''}`}
+      aria-hidden="true"
+    >
+      <span />
+      <span />
+      <span />
+    </span>
+  );
+}