4.3 Address (slug), subdomain and QR

In the Address card, set the slug (2–40 chars, lowercase/hyphens). The page lives at
.../p/the-slug. The editor shows live availability and validates the format.
Custom subdomain (Pro+ plans): turn it on to also serve the page at 
the-slug.rezvy.app.
(Needs DNS/TLS on the platform side.)
The slug can be changed once a week (the editor shows the next allowed date).
Each store has a direct link and a QR code (the QR button) with Download and
Print options — ideal for the counter, window or cards.
📸 
04-address-qr.png — Address card (slug + subdomain toggle) and the QR popup.