Either party can propose a milestone on an active or funded escrow.
The creator auto-approves their own proposal. The other party must call
POST /milestone-approve to lock it, or POST /milestone-request-changes to push it back.
The sum of all accepted milestone amounts must not exceed the escrow total.
JWT access token obtained from /auth-verify (login context) or /auth-signup. Set the bearer_token environment variable in your API client to apply it globally.