Custom Shopify Discount Level Add-On

I need a small, focused Shopify add-on that lets me run three percentage-based Discount Level Codes—A, B, and C. Core requirements • Create and store the three DLCs (A, B, C). • Let me enter a unique percentage discount for every product under each DLC. • Allow me, and only me, to link a customer account to one DLC through the admin. • Customers must sign in with their email; once logged in they see both the original price and their discounted price, and checkout is always at that discounted price. The tool should allow me to apply DLC to all products in the shop. Deliverables 1. Lightweight Shopify app or theme extension that meets the above logic. 2. Admin interface for: – setting the three discount rates per product, – assigning or changing a customer’s DLC. 3. Front-end adjustments so logged-in customers instantly see correct pricing on product pages, the cart, and checkout. 4. Brief setup guide and hand-off call. I’m comfortable installing a private app if that is the cleanest route. Liquid, Polaris, and the latest Shopify API are all fine—use whichever keeps the solution stable and upgrade-friendly.