Point of Sale order lists now show the most recent orders at the top. This makes it easier for staff to find and review the latest transactions without scrolling through older records.

**Description of the issue/feature this PR addresses:**
Show last order on the top in the tree.

Use the same logic of `account.move`  : https://github.com/odoo/odoo/blob/master/addons/account/models/account_move.py#L26


@switch87


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

This fixes an issue where changing the task or project while creating a helpdesk ticket was not reflected on the related timesheet entry. The update helps keep support work, project tracking, and time reporting aligned without manual correction.

Task: https://www.odoo.com/web?#id=2026776&action=327&model=project.task&view_type=form&menu_id=4720
Pad: https://pad.odoo.com/p/r.cf13f687b5e10e960158b568c8b1f558

A display issue in the Mail Enterprise attachment viewer was fixed so attached files are visible again. This helps users open and review attachments without encountering a blank viewer.

With the z-index=-1, attachments are invisible.