AI API Reverse Proxy

Usage:
  OpenAI:    https://api.villo.chat/openai/v1/chat/completions
  Anthropic: https://api.villo.chat/anthropic/v1/messages
  Gemini:    https://api.villo.chat/gemini/v1beta/models/gemini-2.5-flash:generateContent
  GDrive:    https://api.villo.chat/googleapis/drive/v3/files  (OAuth2 token: /oauth2/token)
  Health:    https://api.villo.chat/health
  Status:    https://api.villo.chat/status