This update streamlines how changes to Point of Sale orders are tracked and managed. Previously, changes were handled internally, but now the system calculates and displays order changes directly on the user's device (client-side). This improves responsiveness and reduces server load.

This commit replaces the previous order change tracking mechanism based on `last_order_preparation_change` with two new models: `pos.prep.order` and `pos.prep.line`. All the order changes will be computed on the client side.

Task-5030559