Sign Off Reconciliation

Record your review of a reconciliation for a period. Only a period that reconciles can be signed off, and only by a member of the graph: access that comes from an organization role is not enough. The sign-off records who ran the comparison and who reviewed it, and says so when they are the same person; a reconciliation with separate_reviewer set refuses that case instead. The sign-off stands for the balances as they were compared: if any of them changes afterwards, the period goes back to reconciled or unreconciled and needs signing off again, unless the balances return to the ones already signed. Signing off a period already reviewed changes nothing. Returns the reconciliation's standing for the period.

Idempotency: supply an Idempotency-Key header to make safe retries; replays within 24 hours return the same envelope. Reusing the key with a different body returns HTTP 409 Conflict.