prevent_member_self_role_change covered role/status/space but not the
financial columns; RLS members_update lets a member UPDATE their own
row, so payment_status/dues_paid_until/last_paid_at/last_payment_at/
stripe_customer_id/payment_note/joined_at were self-settable via
PostgREST to forge a dues-good signal. Migration 044 adds them to the
blocked set; service-client (auth.uid() NULL) + privileged-on-another-
member writes still bypass (Stripe webhook unaffected). Schema + maps.
