I need the real-time audio and video calling layer added to both parts of my product: a Flutter mobile app (IOS & Android) , and the companion website that runs on a MERN stack. Both website & app share the same backend. The core requirements are straightforward: • One-to-one and group calls must work seamlessly across mobile and web. • In group calls, participants should be able to share their screen. I am happy to use Getstream io, WebRTC, Agora, or any other free service you prefer, as long as you can wire it into my existing codebases, expose clean APIs, and keep latency low. You’ll be responsible for: – Integrating the SDK or custom WebRTC signaling on both Flutter and Node/React. – UI is done, so you don't have to do – Handling permissions on iOS, Android, and modern browsers. – Delivering clear setup docs and a short walk-through so I can replicate the build. If you have previous live-call projects in Flutter or MERN, let me see a link or short clip—proof of smooth cross-platform performance will move you to the top of the list.