The key to the error message is here:
invalid column name: T1.QuantityUnit
So the view says QuantityUnit doesn't exist in the item table.I can't see your item table to confirm, but perhaps you just have a typo in this column definition when you created the table.
As far as your role, the privilege file looks fine. I believe its actually your role definition which is wrong. You referenced the application privilege as workshop.sessions.system.data::Basic. But your .xsprivileges file is in the project root folder not the data folder and therefore the package path should be workshop.sessions.system::Basic.