Make AutoRAG pip-installable via:
  pip install "autorag[audio,diarize,rag,server] @ git+https://github.com/AutoLogger/AutoRAG@v0.2.0"

- Unified AutoRAG facade in core.py: transcribe, build_agent, persist_transcription, ingest, query
- Heavy deps split into [audio] / [diarize] / [rag] / [server] / [all] extras
- Lazy imports keep base install lightweight