feat(presence): check-in/out + present/attendance actions

Self-only (member resolved server-side, never from input), validated
service-client writes (no client RLS write policy). checkIn enforces
host eligibility via spaces.host_requires_card + active-card count,
blocks a fresh double check-in, and auto-closes a stale open visit
before a new one (handles forgotten check-outs without a cron).
checkOut closes the caller's open visit. listPresentNow (any member;
staleness applied in pure logic), getMyVisits (/me), listAttendance
(all members, last 250). Zod checkIn/checkOut schemas; barrel export.

lib/actions/index.ts

@@ -62,3 +62,6 @@ export * from './member-cards'
 
 // Door connections + executor (Door epic)
 export * from './door'
+
+// Presence & attendance (check-in / check-out / hosting)
+export * from './presence'