feat(web): add /library/liked page with three sections

Each section is its own infinite query against /api/likes/{type}.
Empty sections show 'No liked X yet' (gated on total === 0). Reuses
ArtistRow / AlbumCard / TrackRow for rendering — same components as
the search overflow pages.

web/src/routes/library/liked/liked.test.ts

@@ -0,0 +1,102 @@
+import { afterEach, describe, expect, test, vi } from 'vitest';
+import { render, screen, fireEvent } from '@testing-library/svelte';
+import { mockInfiniteQuery } from '../../../test-utils/query';
+import type { ArtistRef, AlbumRef, TrackRef, Page } from '$lib/api/types';
+import { readable } from 'svelte/store';
+
+vi.mock('$lib/api/likes', () => ({
+  createLikedIdsQuery: () => readable({
+    data: { track_ids: [], album_ids: [], artist_ids: [] },
+    isPending: false,
+    isError: false
+  }),
+  createLikedTracksInfiniteQuery: vi.fn(),
+  createLikedAlbumsInfiniteQuery: vi.fn(),
+  createLikedArtistsInfiniteQuery: vi.fn(),
+  likeEntity: vi.fn(),
+  unlikeEntity: vi.fn()
+}));
+
+vi.mock('@tanstack/svelte-query', async (orig) => {
+  const actual = (await orig()) as Record<string, unknown>;
+  return { ...actual, useQueryClient: () => ({}) };
+});
+
+vi.mock('$lib/api/client', () => ({ api: { get: vi.fn() } }));
+vi.mock('$lib/player/store.svelte', () => ({
+  playQueue: vi.fn(), enqueueTrack: vi.fn(), enqueueTracks: vi.fn()
+}));
+
+import LikedPage from './+page.svelte';
+import {
+  createLikedTracksInfiniteQuery,
+  createLikedAlbumsInfiniteQuery,
+  createLikedArtistsInfiniteQuery
+} from '$lib/api/likes';
+
+function page<T>(items: T[], total: number, offset = 0, limit = 50): Page<T> {
+  return { items, total, offset, limit };
+}
+
+afterEach(() => vi.clearAllMocks());
+
+describe('liked library page', () => {
+  test('renders three sections when each has items', () => {
+    const ar: ArtistRef = { id: 'a1', name: 'X', album_count: 1 };
+    const al: AlbumRef = {
+      id: 'al1', title: 'Y', artist_id: 'a1', artist_name: 'X',
+      year: 2020, track_count: 1, duration_sec: 100, cover_url: '/x'
+    };
+    const tr: TrackRef = {
+      id: 't1', title: 'Z', album_id: 'al1', album_title: 'Y',
+      artist_id: 'a1', artist_name: 'X',
+      track_number: 1, disc_number: 1, duration_sec: 100,
+      stream_url: '/api/tracks/t1/stream'
+    };
+    (createLikedArtistsInfiniteQuery as ReturnType<typeof vi.fn>).mockReturnValue(
+      mockInfiniteQuery({ pages: [page([ar], 1)] })
+    );
+    (createLikedAlbumsInfiniteQuery as ReturnType<typeof vi.fn>).mockReturnValue(
+      mockInfiniteQuery({ pages: [page([al], 1)] })
+    );
+    (createLikedTracksInfiniteQuery as ReturnType<typeof vi.fn>).mockReturnValue(
+      mockInfiniteQuery({ pages: [page([tr], 1)] })
+    );
+    render(LikedPage);
+    expect(screen.getByRole('heading', { name: /artists/i })).toBeInTheDocument();
+    expect(screen.getByRole('heading', { name: /albums/i })).toBeInTheDocument();
+    expect(screen.getByRole('heading', { name: /tracks/i })).toBeInTheDocument();
+  });
+
+  test('empty section renders "No liked X yet" hint', () => {
+    (createLikedArtistsInfiniteQuery as ReturnType<typeof vi.fn>).mockReturnValue(
+      mockInfiniteQuery({ pages: [page<ArtistRef>([], 0)] })
+    );
+    (createLikedAlbumsInfiniteQuery as ReturnType<typeof vi.fn>).mockReturnValue(
+      mockInfiniteQuery({ pages: [page<AlbumRef>([], 0)] })
+    );
+    (createLikedTracksInfiniteQuery as ReturnType<typeof vi.fn>).mockReturnValue(
+      mockInfiniteQuery({ pages: [page<TrackRef>([], 0)] })
+    );
+    render(LikedPage);
+    expect(screen.getAllByText(/no liked/i)).toHaveLength(3);
+  });
+
+  test('Load more calls fetchNextPage on each section that has more', async () => {
+    const fetchTracks = vi.fn();
+    (createLikedTracksInfiniteQuery as ReturnType<typeof vi.fn>).mockReturnValue(
+      mockInfiniteQuery({ pages: [page<TrackRef>([], 100)], hasNextPage: true, fetchNextPage: fetchTracks })
+    );
+    (createLikedAlbumsInfiniteQuery as ReturnType<typeof vi.fn>).mockReturnValue(
+      mockInfiniteQuery({ pages: [page<AlbumRef>([], 0)] })
+    );
+    (createLikedArtistsInfiniteQuery as ReturnType<typeof vi.fn>).mockReturnValue(
+      mockInfiniteQuery({ pages: [page<ArtistRef>([], 0)] })
+    );
+    render(LikedPage);
+    const buttons = screen.getAllByRole('button', { name: /load more/i });
+    expect(buttons).toHaveLength(1);
+    await fireEvent.click(buttons[0]);
+    expect(fetchTracks).toHaveBeenCalledTimes(1);
+  });
+});