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/playback_mode/mod.rs

@@ -20,6 +20,28 @@ pub enum PlaybackMode {
     Idle,
 }
 
+/// Number of Jellyfin ticks per second (100ns units).
+const TICKS_PER_SECOND: f64 = 10_000_000.0;
+
+/// Below this many seconds we treat the position as "at the start" and don't
+/// send a resume position, so a fresh track casts from 0 rather than ~0.
+const RESUME_THRESHOLD_SECONDS: f64 = 0.5;
+
+/// Convert a live playback position (seconds) into the `StartPositionTicks` to
+/// hand to a remote session, or `None` if we're effectively at the start.
+///
+/// Pure helper so the resume-position math is unit-testable without a remote
+/// session or HTTP. The *source* of `position_seconds` matters too: callers
+/// must pass the live backend position (`PlayerController::position()`), not the
+/// snapshot embedded in `PlayerState`, which is stale mid-track on Android.
+fn start_position_ticks_from_seconds(position_seconds: f64) -> Option<i64> {
+    if position_seconds > RESUME_THRESHOLD_SECONDS {
+        Some((position_seconds * TICKS_PER_SECOND) as i64)
+    } else {
+        None
+    }
+}
+
 /// Manages playback mode transfers between local and remote sessions
 pub struct PlaybackModeManager {
     jellyfin_client: Arc<Mutex<Option<JellyfinClient>>>,
@@ -195,7 +217,6 @@ impl PlaybackModeManager {
 
             let queue_arc = player.queue();
             let queue = queue_arc.lock_safe();
-            let state = player.state();
 
             let original_index = queue.current_index().unwrap_or(0);
             let items = queue.items();
@@ -210,7 +231,11 @@ impl PlaybackModeManager {
             }
 
             let (ids, adjusted_index) = self.extract_jellyfin_ids(items, original_index)?;
-            let position = state.position().unwrap_or(0.0);
+            // Read the LIVE backend position, not the snapshot embedded in PlayerState.
+            // On Android the embedded position is only refreshed on play/pause
+            // transitions, so PlayerState::position() is stale (often 0) mid-track;
+            // PlayerController::position() always reflects the backend's current time.
+            let position = player.position();
             let context = queue.context().clone();
 
             log::info!(
@@ -272,12 +297,8 @@ impl PlaybackModeManager {
             }
         };
 
-        // Calculate position in ticks
-        let start_position_ticks = if position_seconds > 0.5 {
-            Some((position_seconds * 10_000_000.0) as i64)
-        } else {
-            None
-        };
+        // Calculate position in ticks (from the live position read above)
+        let start_position_ticks = start_position_ticks_from_seconds(position_seconds);
 
         // Log queue context for debugging (context is tracked but we always send track IDs)
         match &queue_context {
@@ -577,6 +598,23 @@ mod tests {
         );
     }
 
+    /// The resume position handed to a remote session is derived from a live
+    /// playback position. Guards the seconds->ticks conversion and the
+    /// at-the-start threshold (Bug: casting restarted the track from 0).
+    #[test]
+    fn test_start_position_ticks_from_seconds() {
+        // Mid-track positions convert to ticks (10M ticks per second).
+        assert_eq!(start_position_ticks_from_seconds(5.0), Some(50_000_000));
+        assert_eq!(start_position_ticks_from_seconds(123.45), Some(1_234_500_000));
+
+        // At/near the start, send no resume position so the track casts from 0.
+        assert_eq!(start_position_ticks_from_seconds(0.0), None);
+        assert_eq!(start_position_ticks_from_seconds(0.5), None);
+
+        // Just past the threshold resumes rather than restarting.
+        assert!(start_position_ticks_from_seconds(0.6).is_some());
+    }
+
     // Tests for extract_jellyfin_ids - verify all track IDs are sent to remote, not just album/playlist ID
     mod extract_jellyfin_ids_tests {
         use crate::player::{MediaItem, MediaSource, MediaType};