feat(web): wire LikeButton into TrackRow, AlbumCard, ArtistRow, PlayerBar

Heart appears on every entity rendering surface. ArtistRow restructured
to a <div> with the link as a positioned overlay so the heart button
can nest without invalid <button>-in-<a> markup. Shell nav grows a
'Liked' entry pointing at /library/liked.

web/src/lib/components/PlayerBar.svelte

@@ -6,6 +6,7 @@
   } from '$lib/player/store.svelte';
   import { formatDuration } from '$lib/media/duration';
   import { FALLBACK_COVER } from '$lib/media/covers';
+  import LikeButton from './LikeButton.svelte';
 
   const current = $derived(player.current);
 
@@ -48,7 +49,7 @@
           onerror={onCoverError}
         />
       </a>
-      <div class="min-w-0">
+      <div class="min-w-0 flex-1">
         <div class="truncate text-sm font-medium">{current.title}</div>
         <a
           href={`/artists/${current.artist_id}`}
@@ -57,6 +58,7 @@
           {current.artist_name}
         </a>
       </div>
+      <LikeButton entityType="track" entityId={current.id} />
     </div>
 
     <!-- Center: seek row + transport row -->