Security checkpoints + crew QR passes

The Checkpoints tab turns a vessel's gangway, pier gate, or restricted zone into a scan point, and issues every crew member a QR pass they show to come aboard. It's the ship-side equivalent of a building access badge.

Set up a checkpoint:
1. Fleet → Checkpoints → pick the vessel.
2. + Checkpoint → give it a name (e.g. "Gangway — Port"), a kind (Gangway, Pier gate, Restricted zone, or Tender / launch), and optionally a location, a capacity, and a staff instruction shown to the officer on admit.
3. Save. Add as many as the vessel needs.

Issue crew passes:
1. + Issue passes → tick the crew members (they come from your Workforce roster).
2. Issue. Each crew member gets a QR pass good at every checkpoint on that vessel. Crew passes are standing, re-entry passes — scan as many times as needed.
3. Show QR on a pass to display it (the crew member can screenshot it or you can print it).

Scanning people in:
• Open the scanner on a phone (the "Open scanner ↗" link, at /m/scan). The officer picks which checkpoint they're standing at — it's remembered on that device.
• Point the phone camera at a pass QR (or type the code). The QR opens the scanner with the pass pre-filled, so there's no app to install.
• You get a big green ADMIT or red DENY, the holder's name, and any staff instruction. Every scan is decided on the server — capacity, revoked passes, and restricted-zone rules can't be bypassed — and written to the access log.

Aboard status + access log:
"Aboard" is derived from the scan trail — once someone's pass is admitted at the gangway they show as Aboard, with no separate roster to keep. The access log lists recent scans with their decision.

Revoke a pass:
Show QR on a pass → Revoke. The pass stops working immediately at every checkpoint.

Pairs with Voyages — Voyages ▸ Boarding uses the same scanner and the same engine to board paying passengers on a sailing.