feat(revoke): answer a revoke that loses the race with an in-progress response, not "refund already issued" #1522

Problem

When two revoke requests for the same Azure purchase race, the one that loses gets RECONCILE_PENDING ("Refund already issued ... Do not retry", azure_returned: true), while the winning request's Return may still be running. If that Return then fails, nothing was refunded, but the losing caller was told not to retry. Main gives the same answer in that window (the up-front in-flight check); #1520 doesn't change it.

Proposal

Add a distinct response, for example REVOCATION_IN_PROGRESS with azure_returned: false, for a row whose Return is still being posted. Keep RECONCILE_PENDING for rows whose Return Azure has accepted. Update openapi and the frontend copy (the UI owner's part).

Refs #1518, #1520