Create an organization in the connected Auth0 tenant.

Requires editor on the members-organizations module instance (derived from the POST method by the parent router gate). The organization is created natively in Auth0 (the source of truth). The tenant's default all-users username/password connection is enabled without modifying its settings on the new org so members can sign in (best-effort — org creation still succeeds if connection wiring fails). The new organization starts with no members: the creating operator is a platform admin who already belongs to another organization and is deliberately not auto-added.