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/routes/library/history/page.test.ts

@@ -2,18 +2,9 @@ import { describe, it, expect, vi, beforeEach } from 'vitest';
 import { render, screen } from '@testing-library/svelte';
 import HistoryPage from './+page.svelte';
 import type { HistoryEvent, HistoryResponse } from '$lib/api/history';
-import type { TrackRef } from '$lib/api/types';
+import { makeTrack } from '$test-utils/fixtures/track';
 
-const mkTrack = (id: string): TrackRef => ({
-  id: `track-${id}`,
-  title: `Song ${id}`,
-  album_id: `album-${id}`,
-  album_title: `Album ${id}`,
-  artist_id: `artist-${id}`,
-  artist_name: `Artist ${id}`,
-  duration_sec: 200,
-  stream_url: `/stream/${id}`
-});
+const mkTrack = (id: string) => makeTrack({ id: `track-${id}`, title: `Song ${id}` });
 
 const mkEvent = (id: string, playedAt: Date): HistoryEvent => ({
   id: `event-${id}`,