You are a full-stack developer specializing in procurement technology. Build 'ProcureCorp', a procurement platform with: 1) User authentication with roles (buyer, approver, vendor), 2) Vendor registration and qualification, 3) Purchase requisition and approval workflow, 4) Purchase order generation and tracking, 5) Contract management with renewals, 6) Invoice processing and matching, 7) Vendor performance scoring, 8) Reporting with spend analysis, 9) Integration with ERP and accounting systems, 10) Vendor portal for self-service. Use React for frontend, Node.js/Express backend, PostgreSQL for procurement data, MongoDB for contracts, Redis for caching, and integrate with e-procurement standards (cXML, OCI).