Account Invoice Blocking

This module adds a single checkbox called "No Follow-up" to the invoice form in Accounting. It appears right after the fiscal position field on the standard invoice screen.

When you tick the checkbox, the module marks the invoice's receivable or payable lines as blocked. When you untick it, those same lines are unblocked. The checkbox is read-only while the invoice is still in draft state, so you must first confirm the invoice before you can block or unblock it.

The checkbox reflects the status of the underlying lines: it shows as ticked only when every receivable or payable line of the invoice is blocked. If there are no such lines, it stays unticked.

Blocking these lines is meant to prevent them from being picked up by automated processes, for example payment file generation. The module only touches the invoice model (account.move) and its lines; it does not add new menus, reports or scheduled jobs.