Reapply updates from "item price" PR (#577)

[bummytime]

This PR is a dupe of #577 — it re-adds changes from that.

Testing

• Build and run all the unit tests — verify everything is ✅

Here are some suggested testing steps, but feel free to test this however you want.

1. Build and run the app

2. Open the orders tab

3. Find an order with Processing status where the line items have a quantity of 1

4. Open the fullfillment screen

   • Verify the item price and quantity details looks good

5. Find an order with Completed status where the line items have a quantity of 1

6. Open the item details screen

   • Verify the item price and quantity details looks good

7. Find an order with Processing status where the line items have a quantity of 2 or more

8. Open the fullfillment screen

   • Verify the item price and quantity details looks good

9. Find an order with Completed status where the line items have a quantity of 2 or more

10. Open the item details screen

    • Verify the item price and quantity details looks good

[mindgraffiti]

!

[wpmobilebot]

	2 Warnings
⚠️	PR is missing at least one label.
⚠️	Core Data: Do not edit an existing model in a release branch unless it hasn’t been released to testers yet. Instead create a new model version and merge back to develop soon.

Generated by 🚫 Danger