Schema for admin role levels.

• owner/manager are staff who share full back-office access (gated per-page; managers are denied a subset).
• agent is a restricted delivery-driver login that can only ever reach its own logistics run sheet (/admin/deliveries). Auth gates exclude agents from every staff page by default — see sessionRoleAllowed in auth.ts.
• editor is a content-only collaborator: they can create/edit listings and groups and edit the public-site content, but hold no DATA_KEY (so attendee PII is undecryptable for them) and have no ledger/settings/API access. Like agent, they are excluded from every staff page by default and opted in to only the content routes (see CONTENT_ADMIN_LEVELS).