Overview

Reverses the binding of a proposal, restoring it to Accepted status and undoing the changes it applied to the policy. This effectively "un-applies" an endorsement, renewal, or initial quote from the policy, reverting the policy to the state of the prior bound proposal.

What this endpoint does:

1. Loads the proposal by proposalID
2. Validates that the unbind is allowed (permission, status, business rules)
3. Finds the prior bound proposal and re-binds it to restore the policy's previous state
4. Deletes all records created by the original binding (transactions, commissions, invoices, forms, etc.)
5. Reverts the proposal's status from Bound to Accepted
6. Logs the unbind action

Important: This is a destructive operation. It deletes financial records (member transactions, commissions, billing invoices, policy transactions) that were created when the proposal was bound. It cannot be easily reversed.