Permanently deletes a company group. This is a hard delete: the group is removed and cannot be recovered — there is no soft-delete or undo. Returns 404 if no group with that ID belongs to the authenticated company.

Deleting a group also strips it from any price tier that targeted or excluded companies by this group: those price tiers keep working but lose this group from their include/exclude filters. The group is only a label, so deleting it does not delete any customer or vendor relationship that was tagged with it — those companies simply lose the tag.

Required permission: settings_permissions_company_relationship_groups.