Improve Opus decoder error handling with frame skipping

[unforced]

Problem

Currently, if a single Opus frame is corrupted during decoding, the entire recording fails. This is too aggressive and can result in complete data loss.

Location: lib/utils/audio/wav_bytes_util.dart:176-185

Uint8List _processOpus() {
  final decodedSamples = <int>[];
  
  for (final frame in frames) {
    final decoded = _opusDecoder!.decode(input: Uint8List.fromList(frame));
    decodedSamples.addAll(decoded); // Fails entire decode if one frame bad
  }
  
  return _convertToLittleEndianBytes(decodedSamples);
}

Suggested Solution

Skip corrupted frames instead of failing:

Uint8List _processOpus() {
  final decodedSamples = <int>[];
  int skippedFrames = 0;
  
  for (int i = 0; i < frames.length; i++) {
    try {
      final decoded = _opusDecoder!.decode(input: Uint8List.fromList(frames[i]));
      decodedSamples.addAll(decoded);
    } catch (e) {
      debugPrint('[WavBytesUtil] Skipping corrupted Opus frame $i: $e');
      skippedFrames++;
      
      // Insert silence for corrupted frame (20ms at 16kHz = 320 samples)
      decodedSamples.addAll(List.filled(320, 0));
    }
  }
  
  if (skippedFrames > 0) {
    debugPrint('[WavBytesUtil] Skipped $skippedFrames corrupted frames');
  }
  
  return _convertToLittleEndianBytes(decodedSamples);
}

Benefits

• Partial recording recovery instead of complete failure
• Better user experience (some audio > no audio)
• More resilient to BLE transmission errors
• Graceful degradation

Trade-offs

• Introduces brief silence/gaps in audio where frames were corrupted
• Could mask data quality issues if not logged properly

Priority

Medium - Improves robustness for edge cases

Related

• Part of PR #8 review feedback
• Related to Handle BLE disconnection during active Omi recording #10 (BLE disconnect handling)