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The squash-merge of PR #419 was performed against an outdated PR base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

@@ -13,9 +13,11 @@ interface Props {
   moreText?: string;
   onLoadMore?: () => Promise<void>;
   showRating?: boolean;
+  /** Optional content rendered in the row header, left of the scroll-nav. */
+  headerExtra?: React.ReactNode;
 }
 
-export default function AlbumRow({ title, titleLink, albums, moreLink, moreText, onLoadMore, showRating }: Props) {
+export default function AlbumRow({ title, titleLink, albums, moreLink, moreText, onLoadMore, showRating, headerExtra }: Props) {
   const { t } = useTranslation();
   const scrollRef = useRef<HTMLDivElement>(null);
   const navigate = useNavigate();
@@ -71,15 +73,16 @@ export default function AlbumRow({ title, titleLink, albums, moreLink, moreText,
           <h2 className="section-title" style={{ marginBottom: 0 }}>{title}</h2>
         )}
         <div className="album-row-nav">
-          <button 
-            className={`nav-btn ${!showLeft ? 'disabled' : ''}`} 
+          {headerExtra}
+          <button
+            className={`nav-btn ${!showLeft ? 'disabled' : ''}`}
             onClick={() => scroll('left')}
             disabled={!showLeft}
           >
             <ChevronLeft size={20} />
           </button>
-          <button 
-            className={`nav-btn ${!showRight ? 'disabled' : ''}`} 
+          <button
+            className={`nav-btn ${!showRight ? 'disabled' : ''}`}
             onClick={() => scroll('right')}
             disabled={!showRight}
           >