- Add openai package to voice-service requirements
- Add /api/v1/test/tts/synthesize-openai (tts-1/tts-1-hd/gpt-4o-mini-tts)
- Add /api/v1/test/stt/transcribe-openai (gpt-4o-transcribe/whisper-1)
- Add OPENAI_API_KEY and OPENAI_BASE_URL env vars to voice-service
- Flutter test page: SegmentedButton to toggle Local/OpenAI provider
- All endpoints maintain same response format for easy comparison
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>