Legacy events (tickets.enabled=false) with membersOnly=true were
returning a free guest ticket for unauthenticated callers, causing
GET /api/events/[id]/tickets/available to report available:true. The
UI then rendered the registration form and register.post.js 403'd on
submit. Short-circuit early when membersOnly && !hasMemberAccess so the
availability endpoint's existing null-ticketInfo branch surfaces the
correct "members only" reason.
Extracts hasMemberAccess(member) in tickets.js and uses it across event
registration, ticket purchase, and series purchase flows so guest, suspended,
and cancelled records no longer count as members while pending_payment still
does.
