feat(web): TrackRow div+role button with onPlay prop and + queue button

Outer <button> becomes <div role="button" tabindex="0"> with keyboard
handlers (Enter/Space) so a real <button> for + queue can nest without
invalid HTML. New optional onPlay prop overrides the default
playQueue(tracks, index); used by the search Tracks section to call
playRadio(track.id) instead. + queue button calls enqueueTrack and
stops propagation so the row click does not fire.

web/src/lib/components/TrackRow.svelte

@@ -1,25 +1,57 @@
 <script lang="ts">
   import type { TrackRef } from '$lib/api/types';
   import { formatDuration } from '$lib/media/duration';
-  import { playQueue } from '$lib/player/store.svelte';
+  import { playQueue, enqueueTrack } from '$lib/player/store.svelte';
 
-  let { tracks, index }: { tracks: TrackRef[]; index: number } = $props();
+  type PlayHandler = (tracks: TrackRef[], index: number) => void;
+
+  let {
+    tracks,
+    index,
+    onPlay
+  }: { tracks: TrackRef[]; index: number; onPlay?: PlayHandler } = $props();
 
   const track = $derived(tracks[index]);
 
-  function onClick() {
-    playQueue(tracks, index);
+  function activate() {
+    if (onPlay) onPlay(tracks, index);
+    else playQueue(tracks, index);
+  }
+
+  function onRowClick() {
+    activate();
+  }
+
+  function onRowKey(e: KeyboardEvent) {
+    if (e.key === 'Enter' || e.key === ' ') {
+      e.preventDefault();
+      activate();
+    }
+  }
+
+  function onAddClick(e: MouseEvent) {
+    e.stopPropagation();
+    enqueueTrack(track);
   }
 </script>
 
-<button
-  type="button"
-  onclick={onClick}
-  class="grid w-full grid-cols-[32px_1fr_auto] items-center gap-4 px-3 py-2 text-left text-sm odd:bg-surface/50 hover:bg-surface focus-visible:outline focus-visible:outline-2 focus-visible:outline-accent"
+<div
+  role="button"
+  tabindex="0"
+  aria-label={track.title}
+  onclick={onRowClick}
+  onkeydown={onRowKey}
+  class="grid w-full cursor-pointer grid-cols-[32px_1fr_auto_auto] items-center gap-4 px-3 py-2 text-left text-sm odd:bg-surface/50 hover:bg-surface focus-visible:outline focus-visible:outline-2 focus-visible:outline-accent"
 >
   <span class="text-right tabular-nums text-text-secondary">
     {track.track_number ?? '—'}
   </span>
   <span class="truncate">{track.title}</span>
+  <button
+    type="button"
+    aria-label="Add to queue"
+    onclick={onAddClick}
+    class="rounded p-1 text-text-secondary hover:text-text-primary"
+  >+</button>
   <span class="tabular-nums text-text-secondary">{formatDuration(track.duration_sec)}</span>
-</button>
+</div>