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/components/player/VideoPlayer.svelte

@@ -43,6 +43,18 @@
   let videoElement: HTMLVideoElement | null = $state(null);
   let isPlaying = $state(false);
   let currentTime = $state(0);
+  // Guards against onEnded() firing more than once per loaded stream. For
+  // transcoded HLS, both the native `ended` event and the "fatal network error
+  // near end of stream" recovery path can fire for the same playback, which
+  // would otherwise call playerOnPlaybackEnded twice (e.g. decrementing the
+  // sleep-timer episode counter twice). Reset when the stream URL changes.
+  let endedFired = $state(false);
+
+  function notifyEnded() {
+    if (endedFired) return;
+    endedFired = true;
+    onEnded?.();
+  }
   let isFullscreen = $state(false);
   let showControls = $state(true);
   let showSleepTimerModal = $state(false);
@@ -188,6 +200,7 @@
       seekOffset = 0;
       isMediaReady = false; // Reset to loading state when stream URL changes
       hasPerformedInitialSeek = false; // Reset so new video can seek to initial position
+      endedFired = false; // New stream loaded - allow onEnded to fire again
     }
   });
 
@@ -285,9 +298,7 @@
                 if (isNearEnd) {
                   // Near end of stream - treat as natural end, don't restart
                   console.log('[VideoPlayer] Fatal network error near end of stream - treating as ended');
-                  if (onEnded) {
-                    onEnded();
-                  }
+                  notifyEnded();
                 } else if (hlsFatalRecoveryAttempts <= 3) {
                   console.error('[VideoPlayer] Fatal network error, trying to recover (attempt', hlsFatalRecoveryAttempts, ')');
                   hls!.startLoad();
@@ -762,9 +773,7 @@
       onReportStop(currentTime, reportMediaId);
     }
     // Notify parent that video has ended (for next episode popup)
-    if (onEnded) {
-      onEnded();
-    }
+    notifyEnded();
   }
 
   async function togglePlayPause() {