Account Invoice Report Salesperson Info

This module changes the standard invoice PDF so that it shows who the salesperson is for that invoice.

• On the invoice report, a new "Salesperson" block appears inside the invoice information area, next to the other invoice details.
• It shows the salesperson's name and, when available, a phone icon followed by the phone number or the mobile number.
• If the invoice has no salesperson assigned, the block is simply not printed, so nothing empty appears on the document.

The change is applied by inheriting the standard invoice document template (account.report_invoice_document), so it affects the normal invoice PDF generated from the Accounting application. No new menus, buttons, models or automated rules are added: it is purely a report layout change. The information comes from the salesperson already stored on the invoice (invoice_user_id), so no extra data entry is required. Because the same standard template is used for invoices without payment, the salesperson details also appear on that report.