Add LocalAI transcription provider

[JJ-Lin]

Summary

• Adds a LocalAI transcription provider that calls the OpenAI-compatible /v1/audio/transcriptions endpoint.
• Exposes --api localai and documents LOCALAI_BASE_URL, LOCALAI_MODEL, and optional LOCALAI_API_KEY.
• Keeps optional provider imports lazy so direct pytest runs do not require unrelated API SDKs.

Testing

• pytest -q
• .venv/bin/python -m unittest discover -s tests
• .venv/bin/python -m compileall src tests
• git diff --check

This is the companion code change for a Daytona content guide targeting daytonaio/content#13.