fix(android): instant cold-start resume + play button icon flicker

WebBridge: skip setMediaItems/prepare when the track is already buffered
from the cold-start pre-warm, so resuming the last song is instant (~0s)
instead of re-buffering from scratch (~10s).

Player: show pause icon during buffering (isPlaying=false, isBuffering=true)
so the button doesn't flash back to "play" between tracks. Also optimistically
set _nativePlaying=true and call setPlayIcon immediately on playCurrent so the
icon updates before the native callback round-trip.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

android/app/src/main/kotlin/com/novasonic/app/WebBridge.kt

@@ -28,11 +28,20 @@ class WebBridge(private val controllerProvider: () -> MediaController?) {
         runOnMain {
             val ctrl = controllerProvider() ?: return@runOnMain
             val idx = startIndex.coerceAtLeast(0)
-            ctrl.setMediaItems(items, idx, 0L)
-            // Pre-warm artwork before prepare()/play() so the notification bitmap
-            // cache is populated before Media3 renders the first notification.
-            MusicService.instance?.publicWarmArtwork(idx)
-            ctrl.prepare()
+            // If ExoPlayer already has this exact single track buffered from the cold-start
+            // pre-warm, skip setMediaItems+prepare so we don't throw away the buffered data.
+            // Just call play() — this makes the "resume last track" instant instead of ~10s.
+            val alreadyReady = items.size == 1 &&
+                ctrl.mediaItemCount == 1 &&
+                ctrl.currentMediaItem?.mediaId == items[0].mediaId &&
+                ctrl.playbackState != Player.STATE_IDLE
+            if (!alreadyReady) {
+                ctrl.setMediaItems(items, idx, 0L)
+                // Pre-warm artwork before prepare()/play() so the notification bitmap
+                // cache is populated before Media3 renders the first notification.
+                MusicService.instance?.publicWarmArtwork(idx)
+                ctrl.prepare()
+            }
             if (autoPlay) ctrl.play()
         }
     }