Cross-Platform iOS & Android App Build

I need a mobile application that runs smoothly on both iOS and Android. The core idea is ready; what I now require is full development—from architecture and UI/UX through coding, testing, and store deployment.

Key points
• Native-like performance on both platforms (React Native, Flutter or similar cross-platform frameworks are welcome).
• Clean, well-documented code that I can maintain or pass to another team later.
• Submission to the Apple App Store and Google Play, including help with certificates, screenshots, and compliance forms.

Deliverables
1. Source code in a private Git repository.
2. Compiled builds ready for TestFlight and internal Android testing.
3. Final, approved releases live in both stores.
4. A brief hand-over guide covering environment setup, build commands, and any third-party services used.

Acceptance criteria
• App passes store reviews without rejected items.
• No critical or high-severity bugs in the latest OS versions.
• Load time under three seconds on mid-range devices.

Please outline your proposed tech stack, timeline, and any similar apps you have shipped so I can gauge fit and move forward quickly.