[FIX] pos: Negative payment (refund) on touchscreen
[FIX] pos: Negative payment (refund) on touchscreen

currently, if a user wants to return fund to the customer.
we don't have a button to bill negatively. that will fixed.

Task-ID: 1929650
Closes: #31054

Signed-off-by: Quentin Lejeune (qle) <5d1c09880ce30fdcf63039932dac0c183ef0bdc7@odoo.com>
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo