Delete a company

Removes a company from the account: it stops appearing and stops being billed.

• Existing invoices: those already issued are retained, but the company-scoped API can no longer resolve them once the NIF is removed.
• What blocks removal: a NIF activated in Live (409 COMPANY_ACTIVE_IN_PRODUCTION), one holding any invoice in Live — issued, draft or proforma (409 COMPANY_HAS_INVOICES) — and the account's primary NIF (400 CANNOT_DELETE_PRIMARY).
• Deactivating first: switching off in Live is scheduled to the end of the paid cycle, so the removal only becomes possible once that takes effect.
• Test: NIFs never activated, or activated only in Test, are removed right away, and invoices in Test never block.
• Idempotency-Key: without one, a retry after a timeout answers 403 instead of the original 204.