What Checkin is — tap-to-do placards

Checkin is a tiny but cross-cutting primitive: a printable NFC + QR placard that, when tapped, runs an action against whatever module the placard was bound to.

What it powers:
• **Restaurant** — table placard, guest taps to open a check or join a wait list.
• **Lodging** — front-desk QR for self-check-in; a placard on the door for amenity request.
• **Events** — gate placards that admit a ticket holder.
• **Property** — maintenance QR on equipment; tap to log a fault.
• **Generic** — anything else you want a "tap here" surface for.

What you get:
1. A printable PNG of the placard (QR + small label, sized for 3x5 / business card / table tent).
2. An NFC payload you can write to an NFC sticker (any NFC-writer app).
3. A public tap URL — `/checkin/:orgId/:token` — that anyone can hit with no login.
4. Realtime activity stream of every tap.

Operators only see Checkin in their org context. The tapper experience is public.