Node.js + Flutter Dev — Phase 1 Hardening of a Real-Money Betting/Gambling Game (Prototype → Stable)

I have a working prototype of a real-money betting/gambling multiplayer mobile game — players join staked, real-time tournaments and the winner takes the pot minus a house fee. I want to start with a well-defined Phase 1 to make it stable and reliable... (Budget: €750 - €1500 EUR, Jobs: Android, Backend Development, Dart, Flutter, Game Development, Mobile App Development, MySQL, Node.js, Payment Gateway Integration, Socket IO)