Introduces /community-guidelines and /policies/{privacy,terms,[slug]} pages,
swaps the signup/invite checkbox from agreedToTerms to agreedToGuidelines,
adds Member.agreement.acceptedAt, and stamps the field when a Helcim
customer is created.
Admin interface to review, filter, and batch-invite the 95 pre-registrants
from Baby Ghosts. Accept-invitation page pre-fills their data and collects
circle, pronouns, motivation, contribution tier, and agreement before
creating their member record.
