fix: restore audio refactor + features lost in #419 squash-merge (#429)

The squash-merge of PR #419 was performed against an outdated PR base
that predated several main-side refactors and features. The resulting
squash inadvertently re-introduced files that had already been removed
(`src-tauri/src/audio.rs` monolith, `app-icon.png`) and reverted main's
content for ~20 files (`src-tauri/src/lib.rs` decompose, `src/App.tsx`
animation-pause, `src/components/AlbumRow.tsx` headerExtra, etc).

This commit:

* Restores all collateral-damage files to their pre-#419 main state
  (5662dafe), including the audio module split, lib decompose,
  Cargo.toml `windows` dep, animation-pause-on-blur logic, and
  `reducedAnimations` toggle plumbing in WaveformSeek/Settings.
* Keeps the genuine #419 work intact: tri-state duration toggle,
  position counter, persistent Now Playing collapse, animated EQ
  indicator (in QueuePanel.tsx, 8 locales, authStore, components.css).
* Merges authStore.ts so both `reducedAnimations` (from #426) and
  `queueNowPlayingCollapsed` (from #419) coexist.
* Adds the `.eq-bars.paused` CSS rule manually since components.css
  needed a 5662dafe base + the single #419 addition.
* Fixes a latent type error in OverlayScrollArea.tsx (`useRef<T>(null)`
  is `RefObject<T>` / read-only under current `@types/react`; widened to
  `useRef<T | null>(null)` so the existing `wrapRef.current = el`
  assignment compiles).

Verified locally with `cargo check` and `npm run build` — both green.

src/App.tsx

@@ -580,6 +580,25 @@ function AppShell() {
     return () => document.removeEventListener('visibilitychange', update);
   }, []);
 
+  // Pause cosmetic animations when the window loses OS focus but stays visible
+  // (alt-tab, click into another app). On low-VRAM laptops WebView2 keeps
+  // compositing mesh blobs / waveform / marquee at full rate even though the
+  // user isn't looking — measurable GPU drain reported in issue #334.
+  useEffect(() => {
+    const update = () => {
+      const blurred = !document.hasFocus();
+      window.__psyBlurred = blurred;
+      document.documentElement.dataset.appBlurred = blurred ? 'true' : 'false';
+    };
+    window.addEventListener('focus', update);
+    window.addEventListener('blur', update);
+    update();
+    return () => {
+      window.removeEventListener('focus', update);
+      window.removeEventListener('blur', update);
+    };
+  }, []);
+
   const isMobilePlayer = isMobile && location.pathname === '/now-playing';
 
   return (