Start Transcription button now shows the error message when it fails
instead of silently reverting. Common causes:
- Missing PortAudio library on Linux
- Audio device not accessible
- Deepgram connection failure
Also added error details to backend console output and captured
the last error from the Deepgram engine for better diagnostics.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>