feat(library): genre sliders, artist links, and navigation utils

- music landing: diverse per-genre album sliders (online counts /
  offline wide-probe fallback) and home-screen library shortcuts
- add ArtistLinks component and shared navigation/genreDiversity utils
- player/playback-mode refinements across Rust and frontend

src/lib/stores/appState.ts

@@ -6,10 +6,8 @@ import { writable } from 'svelte/store';
 export const isInitialized = writable(false);
 export const pendingSyncCount = writable(0);
 export const isAndroid = writable(false);
-export const shuffle = writable(false);
-export const repeat = writable<'off' | 'all' | 'one'>('off');
-export const hasNext = writable(false);
-export const hasPrevious = writable(false);
+// Shuffle/repeat/next/previous state now lives in the event-driven queue store
+// ($lib/stores/queue), the single source of truth.
 export const showSleepTimerModal = writable(false);
 
 // Library-specific state