Cross-Platform Secure Crypto Wallet

I’m building a non-custodial crypto wallet that runs seamlessly on Android, iOS, a responsive web app, and as a Chrome browser extension. Security leads every decision on this project, so the architecture, codebase, and user flows must be hardened from day one.

The wallet must generate and store private keys locally, let users view balances, sign and broadcast transactions, and switch easily between the four platforms while sharing one secure account. A clean, intuitive interface is important, yet always subordinate to rock-solid protection.

Key security requirements
• Two-Factor Authentication (time-based tokens or comparable)
• Biometric gating where hardware permits (FaceID, TouchID, Android Biometrics)
• Multi-signature support for high-value transfers
• Fully non-custodial design—keys never leave the user’s device

Deliverables include ready-to-publish Android and iOS builds, a production-ready web app, the Chrome extension package, well-commented source code, and a concise deployment guide. I’ll supply preliminary UI mock-ups; your role is to turn them into a polished, responsive experience and integrate the blockchain logic behind the scenes.

Please outline your preferred tech stack, any prior wallet or fintech security experience, and a realistic timeline from kickoff to store submission. I’m looking for a developer or team that treats security as a culture, not a feature.