Version - 17.0

Issue:
- When creating and confirming an alternative sale order (SO) from an upsell order, attempting to generate an invoice would raise a deferred end date error
- As a result, the invoice was not created, and even though the customer's payment succeeded, no invoice was issued.

Steps to reproduce:
- Create an upsell order of a subscription.
- Click Create Alternative to generate an alternative SO.
- Confirm the SO and click on Create Invoice to make the invoice
- This will throw an error of defferred end date

Cause:
- The `next_invoice_date` was not copied from the previous upsell order to the new alternative SO.
- Without this value, the deferred end date was incorrectly computed as today’s date - 1, triggering the error.

Fix:
- Copy the `next_invoice_date` from the previous upsell order to the new alternative SO to ensure proper deferred date computation.

Impact:
Invoices for alternative upsell sale orders can now be created successfully without errors.

task-5241150

Forward-Port-Of: odoo/enterprise#99919
Forward-Port-Of: odoo/enterprise#98983