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/TrackRow.svelte

@@ -2,6 +2,7 @@
   import type { TrackRef } from '$lib/api/types';
   import { formatDuration } from '$lib/media/duration';
   import { playQueue, enqueueTrack } from '$lib/player/store.svelte';
+  import LikeButton from './LikeButton.svelte';
 
   type PlayHandler = (tracks: TrackRef[], index: number) => void;
 
@@ -41,12 +42,13 @@
   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"
+  class="grid w-full cursor-pointer grid-cols-[32px_1fr_auto_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>
+  <LikeButton entityType="track" entityId={track.id} />
   <button
     type="button"
     aria-label="Add to queue"