B2B distribution ERP for Green Biotech, a veterinary-medicine distributor, built on Express + React (TypeScript, Drizzle ORM, PostgreSQL). Customers are shops grouped into territories, each owned by a salesman. The system covers sales orders, invoices, payment collection, returns and refunds, procurement and purchase orders, stock, employees and accounting with journal entries, a ledger, a trial balance and reports. It is a ground-up rebuild of the earlier Spring Boot + React version, designed around the ledger as the single source of truth and strict, tested business rules.