A few seconds of a couple saying "thanks for being here" — that's a different kind of opener than a static welcome message. Hosts can now upload an optional welcome video that plays above the photo grid on the guest view.
Same upload mechanics as photos: drag-and-drop on the host detail page, full resolution preserved, stored in a separate Storage bucket so welcome clips don't mingle with guest uploads. Replacing the video uses a write-new-then-cleanup-old ordering so the gallery never goes blank during the swap.
The welcome message and the welcome video are independent — use one, both, or neither.
