Authenticate to the Netlify REST API (personal access token or OAuth2) and handle rate limits

Documented steps

1. For scripts and CI, create a personal access token: User settings > Applications > Personal access tokens > New access token (optionally with an expiration). Send it on every request as 'Authorization: Bearer <TOKEN>'.
2. For apps acting on behalf of other users, register an OAuth application and send users to https://app.netlify.com/authorize; use the returned access_token in the same Bearer header.
3. Watch the rate-limit headers on every response: X-RateLimit-Limit, X-RateLimit-Remaining, and X-RateLimit-Reset (Unix timestamp when the window resets).
4. On HTTP 429, wait until X-RateLimit-Reset before retrying; add exponential backoff for busy loops.
5. Docs: https://docs.netlify.com/api-and-cli-guides/api-guides/get-started-with-api/