Fix Angular 20 + ASP.NET Web API 2 ERP Performance Issues (Post-Upgrade Slowdown)

We recently upgraded our ERP system's frontend to Angular 20.3.19 and backend to ASP.NET Web API 2 and .Net Framework 4.7.2 Since the upgrade, the application has become noticeably slower — page loads, data grids, and API response times have all degraded compared to the previous version... (Budget: $30 - $250 USD, Jobs: Angular, AngularJS, ASP.NET, Full Stack Development, Microsoft SQL Server, NoSQL Couch & Mongo, Performance Tuning, Web API)