API authentication

1. Browser and public SDK calls use X-ErrorNotifier-Key with the project public key.
2. Server-side release, deploy, and artifact calls use Authorization: Bearer <secret key>.
3. REST namespace: /wp-json/errornotifier/v1.
4. Create reusable domain proof with POST /domain-verifications, GET /domain-verifications/{id}, and POST /domain-verifications/{id}/check.
5. Create events with POST /store or /envelope.
6. Create releases with POST /releases and deploys with POST /deploys.

curl -H "X-ErrorNotifier-Key: enpk_xxx" -d "{\"message\":\"test\"}" /wp-json/errornotifier/v1/store