I need a full-stack developer who can turn my concept for a secure audio- and video-calling service into a polished, production-ready app on both Android and iOS. The core experience must feel crystal-clear on every call, so please lean on WebRTC (or a comparable engine) to guarantee high-definition quality even on moderate bandwidth. Security sits above everything else: all voice, video and chat traffic has to be end-to-end encrypted, and every new session must be protected by two-factor authentication. I am open to Google Authenticator, SMS or push-based 2FA—whichever integrates cleanly with the chosen backend. A built-in coin system will power monetisation. Users should be able to: • top up coins through standard in-app purchase APIs, • spend coins per minute of call or to unlock premium stickers, and • view real-time balances and detailed usage history. Please design the data model so I can tweak prices and payout ratios from an admin panel without redeploying the app. UI/UX needs to stay lightweight, modern and consistent across Kotlin-based Android and Swift/SwiftUI-based iOS builds. Reusable shared logic is welcome if it speeds delivery, but native feel on each platform is non-negotiable. Deliverables include: 1. Source code for both apps and the server components, well commented and ready for hand-off. 2. A small admin dashboard (web or mobile) to manage users, coin pricing and basic analytics. 3. Deployment guides and one live test build on TestFlight and Google Play Internal Testing, showing encrypted calls, 2FA onboarding and a complete coin purchase-spend-balance cycle. Once the above passes functional testing, we can discuss polishing extras such as screen sharing and in-app messaging, but they are optional for the first milestone.