Deactivate ACH links after full payment

For existing non-ACH Stripe links, they are deactivated once they are paid in full.

We should also do this for our new ACH Stripe links. We should deactivate ACH links that are correctly paid in full, and likely on overpayment as well.

Reference how existing non-ACH Stripe links for an example.

Additionally, Stripe checkout links (what we use for ACH) expire after 24 hours. We could add a ttl/expiresAt time to entries in the payment links table, and also check this for whether we should deactivate a Stripe link.

Start by finding the existing deactivation path for non-ACH Stripe links and compare it with the ACH checkout-link flow. Review the payment links table to determine how ttl or expiresAt would fit, then verify that correctly paid, overpaid, and expired ACH links are deactivated as intended.

Rédigé par le modèle d'indexation à partir du texte de l'issue.