Flutter App Update and Deployment

I have 4 Mobile Apps were built with flutter. But those are old version, so I want to update it and redeploy on Apple Store. Should be build/compile on IOS 26+ and need to be submitted on TestFlight of Apple Store seamlessly... (Budget: €250 - €750 EUR, Jobs: App Design, App Development, App Store Optimization, Continuous Integration, Dart, Flutter, iOS, iOS Development, Mobile App Development)