Music player feature for Flutter App

Hi, we need to implement a music player feature with a basic redesign for an existing Flutter app -> [login to view URL] The music player should work well - on iOS and Android - when running in the background (when app is not in the foreground) - when screen is locked - have an offline (download feature) on both platforms. The player widget should be reusable and decoupled with the existing codebase. Technical requirements, UX flow document, user interface design and dart package suggestions would be provided when the project is awarded. However, we are open to your ideas, suggestions & creativity. Looking for freelancers with decent Flutter development experience and portfolio - can turn into a long term / payroll contact based on performance. Lesser preference would be given to agencies. Basic design requirements are hereby attached.