Point of Sale payment and session forms now prevent users from changing fields that should not be modified after creation or processing. This helps keep transaction and session records accurate by removing edit options where changes could cause inconsistencies.

Description of the issue/feature this PR addresses:
The user was able to modify some fields in the pos_payment and pos_session.
Current behavior before PR:
Some fields were editable.
Desired behavior after PR is merged:
The fields are now readonly in the form view and the edit button has been removed.

Task id: 2394740

The manufacturing order screen no longer shows the start button when an order has been cancelled. This prevents users from accidentally trying to begin work on orders that should no longer be processed.

- Hide start button if the MO is cancelled

Task ID: 2443977

Fleet users can now access vehicle forms without errors when payroll-related tax deduction details are calculated. This prevents interruptions for users managing company vehicles and keeps Belgian payroll fleet workflows running smoothly.

An access right error is raised when the tax_deduction field is computed.