fix(android): scrobble respects 1/3 & 2/3 again; no settings flicker on open

Scrobble timing: at onMediaItemTransition ctrl.duration is still TIME_UNSET (→0),
so getScrobbleDelayMs's third/two_thirds modes hit the 15s floor and scrobbled way
too early (both Navidrome + our play-log). Use the song's KNOWN duration
(song.duration), falling back to the player only if absent. Web was unaffected
(it already used the song's duration).

Settings flicker: the ViewModel started with default state (theme = Dark Ocean)
and rendered a frame before DataStore emitted the real values, so the theme picker
visibly jumped. Gate the form on a 'loaded' flag set after the first emit; show a
spinner until then.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

android/app/src/main/kotlin/com/novasonic/app/player/PlayerController.kt

@@ -315,7 +315,11 @@ class PlayerController(private val context: Context, private val repo: MusicRepo
             val mediaId = ctrl.currentMediaItem?.mediaId ?: return
             if (mediaId.startsWith("abs:")) return
             val song = queue.getOrNull(ctrl.currentMediaItemIndex) ?: return
-            val dur  = ctrl.duration.coerceAtLeast(0)
+            // Use the song's KNOWN duration — at a media transition ctrl.duration is still
+            // TIME_UNSET (→0), which collapsed the 1/3 / 2/3 modes to the 15s floor and scrobbled
+            // far too early. Fall back to the player only if the song has no duration.
+            val songDurMs = (song.duration?.toLong() ?: 0L) * 1000L
+            val dur = if (songDurMs > 0) songDurMs else ctrl.duration.coerceAtLeast(0)
             scheduleScrobble(song, dur)
             scope.launch { runCatching { repo.saveLastSong(song) } }
             prefetchLyrics(song)

android/app/src/main/kotlin/com/novasonic/app/ui/screen/SettingsScreen.kt

@@ -67,6 +67,15 @@ fun SettingsScreen(onOpenStats: () -> Unit = {}) {
         )
     }
 
+    // Wait for the persisted settings before drawing the form — otherwise the default state
+    // (e.g. theme = Dark Ocean) flashes for a frame and then jumps to the real values.
+    if (!state.loaded) {
+        Box(Modifier.fillMaxSize(), contentAlignment = Alignment.Center) {
+            CircularProgressIndicator(color = NsAccent)
+        }
+        return
+    }
+
     Column(
         verticalArrangement = Arrangement.spacedBy(12.dp),
         modifier = Modifier

android/app/src/main/kotlin/com/novasonic/app/viewmodel/SettingsViewModel.kt

@@ -35,6 +35,7 @@ data class SettingsUiState(
     val absUrl: String              = "",
     val absApiKey: String           = "",
     val absChapterTrackMode: Boolean = false,
+    val loaded: Boolean             = false,
     val isSaving: Boolean           = false,
     val savedOk: Boolean      = false,
     val error: String?        = null,
@@ -66,6 +67,7 @@ class SettingsViewModel(app: Application) : AndroidViewModel(app) {
                     absUrl              = s.absUrl,
                     absApiKey           = s.absApiKey,
                     absChapterTrackMode = s.absChapterTrackMode,
+                    loaded              = true,
                 )
             }
         }