scrobble: send now playing once per track change

A track transition resets the player position, and the scrobble policy's restart heuristic (same song, position drops to ~0) then re-announced the track we just left and, when the new track's position jittered back to zero, announced it twice. Suppress the now-playing when the restart is the same song; the submission logic still resets so a genuine replay is scrobbled again.

app/src/main/kotlin/com/subtracks/playback/Scrobbler.kt

@@ -59,6 +59,7 @@ class ScrobblePolicy(
             item?.id != songId ||
                 (item != null && item.id == lastItemId && positionMs < previousPosition && positionMs <= RESTART_POSITION_MS)
         if (restarted) {
+            val sameSong = item != null && item.id == songId
             songId = item?.id
             lastItemId = null
             playedMs = 0
@@ -68,7 +69,7 @@ class ScrobblePolicy(
             if (item == null || !isPlaying) return null
             nowPlayingSent = true
             startedAt = now()
-            return Scrobble.NowPlaying(item.id)
+            return if (sameSong) null else Scrobble.NowPlaying(item.id)
         }
         lastPositionMs = positionMs
         lastItemId = item?.id