Create Wholesale Template

Mint a new wholesale provisioning template (PRO-2309): a signup_plan_config row with plan_tier = wholesale_client, seeded from the base wholesale template (or clone_from_plan_id) and then customized in the Signup Provisioning editor.

Read-only snapshot of the tier's provisioning template, composed from the tier's signup plan config (features/flags/team management actions) and the plan's provider channel restrictions.