Everything from this unit
Write the orders controller: validated input, typed ids, meaningful errors, and a guard for the kitchen-only status change.
Test the unhappy paths
An orders API is only trustworthy if it fails well. Before calling the project done, send the requests a careless or hostile client might: an empty items list, a quantity of zero, a dish id that doesn't exist, a status change without the kitchen header, and an id like abc in the URL.
Each should fail with a precise status: 400 for bad shapes and ids, 404 for unknown orders or dishes, 403 for the wrong role. If any of them returns 500 or, worse, succeeds, a rule is missing from a DTO, pipe, guard or service. Fix it in the layer that owns that rule.