Release 1.0.1 — lock invoices transmitted to the PDP

Once an invoice has been transmitted to the PDP (Factur-X e-invoicing), it is legally
immutable. The module now rejects BILL_DELETE / BILL_UNVALIDATE / BILL_MODIFY on such an
invoice, keyed on a new read-only 'dyapiconnect_transmitted' extrafield created at install
that DyaPi sets once the invoice reaches the platform.

See ChangeLog.md for details.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
