refactor(fullscreen-player): H5 — split FullscreenPlayer.tsx 911 → 228 LOC across 11 files (#668)

* refactor(fullscreen-player): H5 — extract FsLyricsApple + FsLyricsRail + useWordLyricsSync

The two lyrics views become own files under components/fullscreenPlayer/.
Their identical word-sync imperative DOM-update useEffect (only differing in
the .fsa-/.fsr- class prefix) collapses into the shared useWordLyricsSync
hook with a classPrefix arg.

FullscreenPlayer.tsx: 911 → 613 LOC.

* refactor(fullscreen-player): H5 — extract FsArt + FsPortrait + FsSeekbar

The three visual subcomponents move into own files. formatTime moves into
utils/fullscreenPlayerHelpers.ts so FsSeekbar keeps using it.

FullscreenPlayer.tsx: 613 → 421 LOC.

* refactor(fullscreen-player): H5 — extract FsLyricsMenu + FsPlayBtn

The lyrics-settings popover and the isolated play/pause button move into
own files. FullscreenPlayer drops the now-unused lucide-react icons
(Play/Pause/Moon/Sunrise/Music) and the PlaybackDelayModal +
PlaybackScheduleBadge imports — both used only by FsPlayBtn now.

FullscreenPlayer.tsx: 421 → 304 LOC.

* refactor(fullscreen-player): H5 — extract useFsDynamicAccent + useFsArtistPortrait + useFsIdleFade

Pulls three state+effect islands out of FullscreenPlayer:
  - useFsDynamicAccent owns the cover-blob fetch + extractCoverColors call
    plus the module-level artKey → accent cache that makes same-album song
    switches instant.
  - useFsArtistPortrait fetches getArtistInfo().largeImageUrl for the right-
    side portrait, returning '' until resolved (or when no artistId).
  - useFsIdleFade flips isIdle true after 3 s of inactivity, exposes a
    throttled mousemove handler, and binds Escape to the provided callback.

FullscreenPlayer.tsx: 304 → 228 LOC.

src/utils/fullscreenPlayerHelpers.ts

@@ -0,0 +1,6 @@
+export function formatTime(seconds: number): string {
+  if (!seconds || isNaN(seconds)) return '0:00';
+  const m = Math.floor(seconds / 60);
+  const s = Math.floor(seconds % 60);
+  return `${m}:${s.toString().padStart(2, '0')}`;
+}