TikTok-Style Video App Build

I am building an application patterned after TikTok or Facebook, with video-sharing as the core feature. The goal is a polished mobile experience (iOS and Android) where users can record, upload, browse, like, and comment on short videos in a continuously scrolling feed.

Scope
• End-to-end development: technical architecture, UI/UX, coding, testing, and deployment to both app stores.
• Core modules first: account creation, secure login, fast video capture/upload (FFmpeg or similar), adaptive streaming, reaction system, and an algorithmic feed.
• Optional next phase: direct messaging and broader social-post features once the MVP proves stable.

Tech Expectations
A modern cross-platform stack such as Flutter or React Native tied into a real-time backend (Firebase, AWS Amplify, or your proven alternative) fits the project well, but I’m open to suggestions if they ensure smooth video delivery and horizontal scalability.

Deliverables
1. Clickable design prototype for approval.
2. Complete, documented source code.
3. Step-by-step build & deployment guide.
4. Post-launch support window for bug fixes.

Please outline the tools you’d use, a realistic timeline with milestones, and any prior work that shows mastery of video pipelines on mobile.