I’m building a customer-service chat similar to WhatsApp and I want it running smoothly on Web, iOS, and Android from a single codebase. Customers must be able to start a conversation, share photos or other files, and—when needed—arrange a quick call or a follow-up message without leaving the app. On my side I need to see every incoming message in real time, receive push notifications on my phone, reply instantly, and keep a searchable history of each chat. Security is a priority: end-to-end encryption for messages, protected media storage, and solid user-access controls are non-negotiable. A clean admin dashboard where I can monitor conversations, tag or schedule contacts for later follow-up, and disable abusive users will make daily work far easier. To keep expectations crystal clear, here’s what I expect as tangible deliverables: • Real-time messaging engine with push notifications • Companion apps for Web, iOS, and Android built from a shared codebase (Flutter, React Native, or similar—open to your recommendation) • Secure file-sharing (images, docs, etc.) with preview inside the chat • Basic call-scheduling or “call me” trigger integrated into each conversation thread • Admin panel for conversation management, user lookup, and chat export • End-to-end encryption and GDPR-ready data handling If you’ve already shipped chat or customer-support platforms, tell me which frameworks you’d lean on and how you’d hit the security requirements. I’m ready to start as soon as we lock in the tech stack and timeline.