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-tauri/src/audio.rs

@@ -2345,8 +2345,8 @@ fn spawn_progress_task(
         let mut samples_played = samples_played;
 
         loop {
-            // 100 ms tick — tight enough for responsive UI, low enough CPU cost.
-            tokio::time::sleep(Duration::from_millis(100)).await;
+            // 500 ms tick — frontend interpolates visually at 60 fps via rAF.
+            tokio::time::sleep(Duration::from_millis(500)).await;
 
             if gen_counter.load(Ordering::SeqCst) != gen {
                 break;