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The squash-merge of PR #419 was performed against an outdated PR base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/components/OverlayScrollArea.tsx

@@ -20,6 +20,8 @@ export type OverlayScrollAreaProps = {
   viewportScrollBehaviorAuto?: boolean;
   /** Ref to the scrollable element (querySelector, scrollIntoView, etc.). */
   viewportRef?: React.Ref<HTMLDivElement>;
+  /** Ref to the outer wrapper (incl. overlay scrollbar rail). */
+  wrapRef?: React.Ref<HTMLDivElement>;
   /** Optional id on the viewport (e.g. main app scroll for route pages). */
   viewportId?: string;
   /** Optional wheel handler on the scrollable viewport. */
@@ -49,11 +51,12 @@ export default function OverlayScrollArea({
   railInset = 'none',
   viewportScrollBehaviorAuto = false,
   viewportRef: viewportRefProp,
+  wrapRef: wrapRefProp,
   viewportId,
   viewportOnWheel,
   viewportOnTouchMove,
 }: OverlayScrollAreaProps) {
-  const wrapRef = useRef<HTMLDivElement>(null);
+  const wrapRef = useRef<HTMLDivElement | null>(null);
   const viewportRef = useRef<HTMLDivElement | null>(null);
   const [meta, setMeta] = useState({ thumbH: 0, thumbT: 0, visible: false });
 
@@ -109,6 +112,11 @@ export default function OverlayScrollArea({
     assignRef(viewportRefProp, el);
   };
 
+  const setWrapNode = (el: HTMLDivElement | null) => {
+    wrapRef.current = el;
+    assignRef(wrapRefProp, el);
+  };
+
   const rootClass = [
     'overlay-scroll',
     RAIL_INSET_CLASS[railInset],
@@ -121,7 +129,7 @@ export default function OverlayScrollArea({
   const viewportClass = ['overlay-scroll__viewport', viewportClassName].filter(Boolean).join(' ');
 
   return (
-    <div ref={wrapRef} className={rootClass} onMouseMove={onMouseMove}>
+    <div ref={setWrapNode} className={rootClass} onMouseMove={onMouseMove}>
       <div
         id={viewportId}
         ref={setViewportNode}