GET /api/providers

{
  "providers": [
    {
      "id": "openai",
      "name": "OpenAI",
      "enabled": true,
      "models": ["gpt-4o", "gpt-4", "gpt-3.5-turbo"]
    }
  ]
}

POST /api/providers

{
  "provider": "anthropic",
  "apiKey": "sk-ant-...",
  "defaultModel": "claude-3-5-sonnet-20241022"
}

PUT /api/providers/default

{
  "provider": "openai",
  "model": "gpt-4o"
}