Sprint 2 stuff

Created by: udoman

-Added Settings page -Added Cashier Settings, Modal for Add, Edit, and Set Cashiers -Added Discount -Implemented local storage for the discount rate and clerk's initials -Implemented Discount rate applied on the invoice when calculating the total -Tried Implementing tax rate based on item category using backend functions (not working) hoping it should work with merge. -Updated add new product Items for Inventory according to the backend schema -Implemented logic for barcode scanning breakdown according to the structure of the meat center -Added input bar to change items by their weight once scanned