refactor: split views.js and ui.js into focused modules

Extract 3 new files from oversized source files:
- src/components.js (~86 lines): makeCard, makeAlbumCard, makeSongItem,
  makeGlobalTrackItem, mkSection — reusable DOM builders
- src/spotify.js (~187 lines): loadSpotifyImporter, resolveSpotifyLink,
  clearSpotifyPreview, spotifyDlAll, and private render/artwork helpers
- src/nowplaying.js (~255 lines): openNowPlaying, closeNowPlaying,
  syncNowPlaying, switchNpTab, full lyrics engine, renderNpQueue,
  npGoArtist/Album, openNpMenu/closeNpMenu

views.js: 1121 → 864 lines
ui.js:     706 → 462 lines

Update imports in main.js, player.js, views.js accordingly.
Build verified: 15 modules, no errors.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/player.js

@@ -3,7 +3,7 @@ import { esc, formatDur, toast } from './utils.js';
 import { api, streamUrl, coverUrl, downloadUrl } from './api.js';
 // views.js/ui.js circular imports — safe (only used inside function bodies)
 import { loadRecommendations } from './views.js';
-import { updateLyricsHighlight, onNpSongChange } from './ui.js';
+import { updateLyricsHighlight, onNpSongChange } from './nowplaying.js';
 
 // ─── PLAYBACK ───
 export function playQueue(songs, startIdx) {