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-tauri/src/player/state.rs

@@ -61,7 +61,12 @@ pub enum PlayerState {
 }
 
 impl PlayerState {
-    /// Get the current playback position if available
+    /// Get the current playback position if available.
+    ///
+    /// Note: this is the position snapshot embedded in the state at the last
+    /// state transition, not the live backend position. For an up-to-date
+    /// value use `PlayerController::position()`.
+    #[allow(dead_code)]
     pub fn position(&self) -> Option<f64> {
         match self {
             PlayerState::Playing { position, .. } => Some(*position),