You are a full-stack developer specializing in FP&A technology. Build 'BudgetCorp', a budgeting platform with: 1) User authentication with roles (finance, department manager, executive), 2) Budget creation with templates and versions, 3) Collaborative forecasting with driver-based inputs, 4) Scenario planning and what-if analysis, 5) Actuals vs budget variance tracking, 6) Rolling forecasts and reforecasting, 7) Reporting with financial dashboards, 8) Integration with ERP and accounting systems, 9) Workflow for budget approvals, 10) Data visualization with charts and tables. Use React for frontend, Node.js/Express backend, PostgreSQL for financial data, Redis for caching, and implement comprehensive calculation engines for financial modeling.