Show deposit release confirmation and scheduled time

Problem: When a security deposit is released, hosts have no easy way to prove it to the guest. Guest-message attachments are only possible for a short window after checkout, so by the time the hold clears the host can't share a screenshot. Hosts also don't see the exact hour the release was scheduled, so they can't set guest expectations upfront. Proposal: Auto-attach the deposit-release confirmation (or a downloadable PSP letter) to the guest message thread when the release fires. Display the exact scheduled release time on the reservation / deposit view.