refactor(web): sweep 24 test files to use makeTrack/makeTracks fixtures (#375)

Replaces inline TrackRef literal redefinitions with calls to the
test-utils helper. Tests that asserted on default field values
(e.g. track titles, artist names rendered in the DOM) keep explicit
overrides; tests that only need a stub for shape now use makeTrack()
with no overrides.

PlaylistCard.test.ts, PlaylistTrackRow.test.ts, and playlist.test.ts
SKIPPED — they use PlaylistTrack (with track_id/added_at), not TrackRef.
ArtistCard.svelte and +page.svelte route files (matched by initial grep)
SKIPPED — live code, not test files.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/src/lib/components/AddToPlaylistMenu.test.ts

@@ -1,7 +1,7 @@
 import { describe, expect, test, vi } from 'vitest';
 import { render, screen, fireEvent, waitFor } from '@testing-library/svelte';
 import { readable } from 'svelte/store';
-import type { TrackRef } from '$lib/api/types';
+import { makeTrack } from '$test-utils/fixtures/track';
 
 const playlistsData = vi.hoisted(() => ({
   owned: [
@@ -69,16 +69,7 @@ vi.mock('$lib/api/playlists', () => ({
 
 import AddToPlaylistMenu from './AddToPlaylistMenu.svelte';
 
-const track: TrackRef = {
-  id: 't1',
-  title: 'Roygbiv',
-  album_id: 'a1',
-  album_title: 'MHTRTC',
-  artist_id: 'ar1',
-  artist_name: 'BoC',
-  duration_sec: 137,
-  stream_url: '/api/tracks/t1/stream'
-};
+const track = makeTrack();
 
 describe('AddToPlaylistMenu', () => {
   test('lists own playlists alphabetically followed by "New playlist…"', () => {