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/routes/+layout.svelte

@@ -17,7 +17,10 @@
   import MiniPlayer from "$lib/components/player/MiniPlayer.svelte";
   import SleepTimerModal from "$lib/components/player/SleepTimerModal.svelte";
   import BottomNav from "$lib/components/BottomNav.svelte";
-  import { isInitialized, pendingSyncCount, isAndroid, shuffle, repeat, hasNext, hasPrevious, showSleepTimerModal } from "$lib/stores/appState";
+  import { isInitialized, pendingSyncCount, isAndroid, showSleepTimerModal } from "$lib/stores/appState";
+  // Shuffle/repeat/next/previous come from the event-driven queue store, the
+  // single source of truth (updated instantly on queue_changed).
+  import { isShuffle as shuffle, repeatMode as repeat, hasNext, hasPrevious } from "$lib/stores/queue";
 
   let { children } = $props();