feat(webchat): add inline audio playback for TTS-generated audio
Implements feature request #3504 - Inline audio playback in WebChat UI
Changes:
- Add InlineAudioParser to detect MEDIA: prefixed paths pointing to audio files
- Add InlineAudioPlayerView SwiftUI component with play/pause controls
- Integrate audio player rendering into ChatMarkdownRenderer
- Add comprehensive unit tests for audio path parsing
Supported audio formats: .mp3, .opus, .m4a, .ogg, .oga, .wav, .aac, .flac
The inline audio player displays:
- Play/pause button
- Audio file name
- Progress bar with duration
- Graceful error handling for missing files
Closes #3504
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