feat(sidebar): toggle to pin Now Playing to the top (#1000)

* feat(sidebar): add toggle to pin Now Playing to the top

The fixed Now Playing entry can now be pinned to the very top of the
sidebar (above the Library label) instead of sitting above the bottom
spacer. Adds a persisted `nowPlayingAtTop` setting (default off, so
existing layouts are unchanged) and a toggle in the sidebar customizer
next to the Mix-navigation split. The entry stays non-hideable and
keeps its playing indicator in both positions.

* i18n(settings): Now Playing-at-top toggle strings (9 locales)

* docs(changelog): note Now Playing top toggle (#1000)

src/locales/es/settings.ts

@@ -373,6 +373,8 @@ export const settings = {
   advancedBadge: 'Avanzado',
   sidebarDrag: 'Arrastra para reordenar',
   sidebarFixed: 'Siempre visible',
+  nowPlayingTopTitle: '"Reproduciendo Ahora" arriba',
+  nowPlayingTopDesc: 'Fijar la entrada "Reproduciendo Ahora" en la parte superior de la barra lateral en lugar de abajo.',
   randomNavSplitTitle: 'Dividir navegación Mix',
   randomNavSplitDesc: 'Mostrar "Mezcla Aleatoria", "Álbumes Aleatorios" y "Mezcla Suerte" como entradas separadas en la barra lateral en lugar del hub "Crear Mezcla".',
   tabInput: 'Entrada',