chore(fullscreen-player): drop dead i18n keys and old CSS (#1002)

Follow-up cleanup after the old fullscreen player was removed (#1001):
- remove the 9 now-unused settings i18n keys (fsPlayerSection,
  fsShowArtistPortrait(+Desc), fsPortraitDim, fsLyricsStyle(+Rail/Apple
  +Descs)) across all 9 locales.
- reduce fullscreen-player-adaptive-portrait.css to the shared lyrics
  overlay styles (FsLyricsApple); drop the old player's .fs-*, the
  .fslm-* lyrics menu, the unused .fsa-fade-* and dead keyframes.

src/locales/zh/settings.ts

@@ -497,15 +497,6 @@ export const settings = {
   infiniteQueue: '无限队列',
   infiniteQueueDesc: '队列播完时自动追加随机曲目',
   experimental: '实验性',
-  fsPlayerSection: '全屏播放器',
-  fsShowArtistPortrait: '显示艺术家照片',
-  fsShowArtistPortraitDesc: '在全屏播放器右侧显示艺术家照片（或专辑封面）。',
-  fsPortraitDim: '照片暗化',
-  fsLyricsStyle: '歌词显示样式',
-  fsLyricsStyleRail: '轨道',
-  fsLyricsStyleRailDesc: '经典5行滑动轨道。',
-  fsLyricsStyleApple: '滚动',
-  fsLyricsStyleAppleDesc: '全屏可滚动列表。',
   sidebarLyricsStyle: '歌词滚动样式',
   sidebarLyricsStyleClassic: '经典',
   sidebarLyricsStyleClassicDesc: '活动行居中显示。',