Add partner reference

This module makes the reference saved on a contact visible directly in the accounting list screens.

• A new column called 'Customer reference' appears in the list views of customer invoices, supplier bills, supplier refunds and customer credit notes.
• The value shown is taken automatically from the 'Reference' field of the contact linked to the invoice; it is not typed on the invoice itself.
• The column is placed just before the partner name and is shown by default, but users can hide it or add it back through the optional columns menu of the list.

It only touches the invoice/journal entry area (account.move) and its list views. No new menus, buttons, checks, emails or scheduled actions are added, and no accounting entries are changed. To use it, fill in the reference on the contact record; the invoices of that contact will then display it in the list.