Function record_audio 

pub async fn record_audio(
    _duration: Duration,
    output_path: &Path,
    config: AudioCaptureConfig,
) -> Result<f32, AppError>

Record audio from the microphone until user stops speaking (4 seconds of silence) Returns the duration of recorded audio in seconds

This function runs the entire recording process in a blocking task to avoid Send/Sync issues with cpal::Stream