After a preparation ticket was marked as completed, transferring one of
its items to another table through Split still kept that item in the
order's kitchen history. When a new product was later added and sent
from the destination table, the preparation display created a new
ticket containing both the new item and the already completed one.

Steps to reproduce:
-------------------
* Open a POS session and the Preparation Display
* Select Table 1, add 2 items and send them to the kitchen
* Mark the preparation ticket as Completed
* On Table 1, open Split, select one item and Transfer it to Table 2
* Open Table 2, add a new item and send it to the kitchen

> Observation:
The new preparation ticket contains the newly added item and the
previously completed transferred item.

Why the fix:
------------
Split and table transfer move preparation history to the destination
order with a new line uuid, but the preparation display still tracks
the original ticket on the source order. Without marking the moved
quantity as already sent, the server treated the transferred line as
pending and included it again in the next ticket.

Set transferredQty when moving preparation history on split/transfer,
and read it reliably in _process_preparation_changes so only items
with a real quantity increase are sent to the kitchen.

Related: https://github.com/odoo/odoo/pull/273568

opw-6146176