perf: reduce CPU usage and unify next-track buffering settings

- Throttle audio:progress from 100ms to 500ms; WaveformSeek and
  FsSeekbar use imperative DOM updates instead of React re-renders
- Fix all usePlayerStore() calls without selectors across pages and
  components (useShallow / individual selectors throughout)
- Remove filter:blur and transform:scale from Hero, AlbumDetail and
  FullscreenPlayer backgrounds — eliminated expensive software
  compositing layers on WebKitGTK
- Replace translate3d with 2D translate in FS mesh and portrait
  animations; remove will-change:transform from mesh blobs
- Move Hot Cache section from Storage tab to Audio tab; group Preload
  and Hot Cache under a shared 'Next Track Buffering' section with a
  mutual-exclusivity note and auto-disable logic
- Add 'off' toggle to Preload (replaces Off button with toggle switch);
  enabling either method now automatically disables the other

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

src/locales/en.ts

@@ -572,6 +572,9 @@ export const enTranslation = {
     gaplessDesc: 'Pre-buffer next track to eliminate gaps between songs',
     preloadMode: 'Preload Next Track',
     preloadModeDesc: 'When to start buffering the next track in the queue',
+    nextTrackBufferingTitle: 'Next Track Buffering',
+    preloadHotCacheMutualExclusive: 'Preload and Hot Cache serve the same purpose — only one can be active at a time. Enabling one will automatically disable the other.',
+    preloadOff: 'Off',
     preloadBalanced: 'Balanced (30 s before end)',
     preloadEarly: 'Early (after 5 s of playback)',
     preloadCustom: 'Custom',