Check-in and badge demo (mock)

This exercises the fixed registration contract against a local mock. It shows the states a volunteer would see: refused with a reason, checked in, already checked in, badge printed, printer offline with retry versus reprint. Nothing here touches a real system.

Your memberships:

• None. A check-in will be refused with reason no_active_membership until an operator approves a join request.

Demo rule: the guest speaker night (ev-3) has an offline printer so you can see failure, retry and reprint.