chore: remove Google provider entirely

update model list by removing deprecated entries and consolidating Google models

clean error messages, add model validation, add gemini-3.1-flash-lite

revert to /v1 prefix with APIRouter

change API prefix to /api/v1 to avoid HF routing conflict

remove APIRouter prefix, hardcode paths

add root endpoint for HF Spaces routing

deploy to HF Spaces: add Dockerfile, remove dashboard

feat: add OpenAI-compatible API proxy with NVIDIA and Google integration