feat(queue): add Timeline display mode (#1004)

* feat(queue): add Timeline display mode

A third queue display mode alongside Queue and Playlist. Timeline shows
the full queue anchored on the current track — played history above
(dimmed), upcoming below — with 'History' and 'Up next' dividers and the
current row auto-centered. It already follows shuffle order since the
queue is stored in play order. The header mode button now cycles
queue → timeline → playlist; Settings gains a third option.

* i18n(queue): Timeline mode strings (9 locales)

* docs(changelog): note Timeline queue mode (#1004)

src/locales/es/queue.ts

@@ -1,6 +1,9 @@
 export const queue = {
   title: 'Cola',
   modePlaylist: 'Lista',
+  modeTimeline: 'Cronología',
+  upNext: 'A continuación',
+  history: 'Historial',
   noUpcoming: 'No hay próximas pistas.',
   savePlaylist: 'Guardar Lista',
   updatePlaylist: 'Actualizar Lista',