fix: set interleaved=true for PcmPlayer streaming playback

FlutterSoundPlayer.feedUint8FromStream() requires interleaved mode.
With interleaved=false, every feed() call threw:
  "Cannot feed with UInt8 with non interleaved mode"

- feedUint8FromStream (Uint8List) → requires interleaved: true
- feedFromStream (Float32List) → requires interleaved: false
Since we feed raw PCM bytes (Uint8List), interleaved must be true.

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

it0_app/lib/core/audio/pcm_player.dart

@@ -53,7 +53,7 @@ class PcmPlayer {
       codec: Codec.pcm16,
       sampleRate: 16000,
       numChannels: 1,
-      interleaved: false,
+      interleaved: true,
       bufferSize: 8192,
     );