### Issue before this commit:
When creating an invoice using the child contact of a parent contact that has a different language with respect to the father, the label of the invoice line was not always displayed in the child contact language but in the father's contact language.

### Steps to reproduce the issue:
1. Activate at least 2 languages (X and Y)
2. Create a product and set the translation for that product in the activated languages
3. Create a Contact with the language X
4. Create a child contact (invoice adress type) for that contact with language Y
5. Create a new invoice setting the customer as the child contact
6. Add the product you created
7. See the label is displayed in the language of the parent contact

### Cause of the issue:
The computation of the invoice line name relied on line.partner_id.lang. However, the partner_id of the move line is automatically set to the commercial partner that can be different (can be the father's contact) to the contact used on the invoice. As a result, the product description was translated using the wrong language.

### Reason to introduce the fix:
To ensure that invoice line labels are correctly translated according to the language of the selected invoice contact, the computation now uses the language of move_id.partner_id instead of line.partner_id. This guarantees consistent and expected behavior in multilingual environments, especially when using different contacts under the same commercial partner.

opw-5955875

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I confirm I have signed the CLA and read the PR guidelines at www.odoo.com/submit-pr

Forward-Port-Of: odoo/odoo#258458
Forward-Port-Of: odoo/odoo#254833

**Steps to reproduce:**
- Set up an event, go put it's state to Annonced
- Set up any online payment method (Demo also triggers the bug)
- Go to a PoS that sells the event tickets
- Purchase one and pay with the online payment method
- Once on the ticket screen, the button to download the event tickets is not displayed

**Why the fix:**
The normal flow only works for offline payment methods, because we check if the ordered is either paid or invoiced before setting all the values needed by the frontend regarding the ticket registration.

The problem is that with an online payment method, once we enter the **read_pos_data** method that sets
the values for the frontend, the order is still in draft, so we just return without doing anything.

We now set the values regardless of the order's status and send the confirmation mail in the same way as if it was an online payment.
In the case of an online payment, the mail will be sent by the **action_pos_order_paid** function that is called once the payment is processed.

A test might be a bit weird to make as we don't have a bridge for pos_online_payment and pos_event, and that we would need to mock the server's answer to be able to pay for the online payment and check that we have the needed values. So the setup for pos_event would have to be copied into pos_online_payment to test it and it would only be ran if both modules are installed.

opw-5438432

Forward-Port-Of: odoo/odoo#249306

Steps to produce:
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- Install the `Sales` module.
- Enable discounts from settings.
- Create a Sale Order with a negative discount on an order line.
- Preview the Sale Order and click on the view details button.

Issue:
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- Negative discount values are not shown in the preview (portal view), but they are displayed in the generated PDF.

Root cause:
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- At [1], the portal template includes a condition to display discounts only when they are greater than 0, while the report templates lack this check, leading to inconsistent behavior.

Solution:
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- Applied the same condition in the report templates to align the PDF output with the portal preview behavior.

Before:
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<img width="787" height="136" alt="image" src="https://github.com/user-attachments/assets/d32311be-4aec-4d6f-b905-d5e52f712ba4" />

After:
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<img width="775" height="139" alt="image" src="https://github.com/user-attachments/assets/2614a8ad-dca6-49ca-b720-5c234aa91cf6" />


[1]https://github.com/odoo/odoo/blob/0f463fd247d2f5da79d6ec2b6bec18774f6f600b/addons/sale/views/sale_portal_templates.xml#L539

Enterprise PR: https://github.com/odoo/enterprise/pull/111916

opw-6061568

Forward-Port-Of: odoo/odoo#258614
Forward-Port-Of: odoo/odoo#255735