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.test.ts

@@ -1,12 +1,28 @@
 import { afterEach, describe, expect, test, vi } from 'vitest';
 import { render, screen, fireEvent } from '@testing-library/svelte';
 import type { TrackRef } from '$lib/api/types';
+import { readable } from 'svelte/store';
 
 vi.mock('$lib/player/store.svelte', () => ({
   playQueue: vi.fn(),
   enqueueTrack: vi.fn()
 }));
 
+vi.mock('$lib/api/likes', () => ({
+  createLikedIdsQuery: () => readable({
+    data: { track_ids: [], album_ids: [], artist_ids: [] },
+    isPending: false,
+    isError: false
+  }),
+  likeEntity: vi.fn(),
+  unlikeEntity: vi.fn()
+}));
+
+vi.mock('@tanstack/svelte-query', async (orig) => {
+  const actual = (await orig()) as Record<string, unknown>;
+  return { ...actual, useQueryClient: () => ({}) };
+});
+
 import TrackRow from './TrackRow.svelte';
 import { playQueue, enqueueTrack } from '$lib/player/store.svelte';