The Role field used json:"role,omitempty". Admin is RoleAdmin = 0, so an
admin profile serialized without a `role` key. The admin-frontend gates the
admin menu (user management, settings) on `role === 0`, and its normalizeRole
helper defaults a missing role to non-admin, so admins lost the admin menu.
Drop omitempty so role 0 is always sent. Add a regression test.
