feat(folder-browser): keyboard nav, context menus, now-playing path UX

Adds full keyboard navigation (arrow keys, Enter, Ctrl+Enter for context menu) across Folder Browser columns. Context menus for all row types with keyboard-operable submenus and star-rating control via arrow keys + Enter. Now-playing path is visually emphasized and stays stable; rebuilds on hotkey re-invoke or active-path follow-along. Adaptive column layout for deep trees with right-side visibility priority. New configurable 'Open Folder Browser' keybinding. StarRating animation sync for keyboard-driven changes. All 7 locales updated.

src/App.tsx

@@ -409,6 +409,7 @@ function AppShell() {
 
 // Media key + tray event handler
 function TauriEventBridge() {
+  const navigate = useNavigate();
   const togglePlay = usePlayerStore(s => s.togglePlay);
   const next = usePlayerStore(s => s.next);
   const previous = usePlayerStore(s => s.previous);
@@ -486,6 +487,9 @@ function TauriEventBridge() {
           break;
         }
         case 'toggle-queue':      toggleQueue(); break;
+        case 'open-folder-browser':
+          navigate('/folders', { state: { folderBrowserRevealTs: Date.now() } });
+          break;
         case 'fullscreen-player': toggleFullscreen(); break;
         case 'native-fullscreen': {
           const win = getCurrentWindow();