introducing floating bar with toggle

src/App.tsx

@@ -145,6 +145,7 @@ function AppShell() {
   const setEntityRatingSupport = useAuthStore(s => s.setEntityRatingSupport);
   const offlineAlbums = useOfflineStore(s => s.albums);
   const hasOfflineContent = Object.values(offlineAlbums).some(a => a.serverId === serverId);
+  const { floatingPlayerBar } = useThemeStore();
 
   // Mini player → main: route requests dispatched as `psy:navigate`
   // CustomEvents from the bridge land here so React Router can take over.
@@ -351,7 +352,7 @@ function AppShell() {
 
   return (
     <div
-      className="app-shell"
+      className={`app-shell ${floatingPlayerBar ? 'floating-player' : ''}`}
       data-mobile={isMobile || undefined}
       data-mobile-player={isMobilePlayer || undefined}
       data-titlebar={(IS_LINUX && useCustomTitlebar && !isWindowFullscreen && !isTilingWm) || undefined}