Build LYRR Cross-Platform Reading App

I am creating LYRR, a secure digital reading and listening experience that must feel identical on Android, iOS, Windows desktop, and through a browser-based administration portal. Users open a book, tap play, and the spoken narration keeps perfect time with the highlighted text; flipping pages or scrubbing the progress bar must never break that sync.

Scope of work
You will design and code the complete solution, package it for each target platform, and wire everything to a single back-end so one account and library follow the reader everywhere. Sign-in for version 1 is email-and-password only, but the architecture should let us add social or SSO providers later without rewriting the core.

Content management and security
The web portal needs role-based access where my team can upload new titles, attach the matching audio, choose whether a book is free, subscription-gated, or paid, and push updates instantly. All assets have to remain encrypted in storage and during delivery, and the app must apply the correct license rules even when a user is offline.

Deliverables
• Android APK, iOS build ready for TestFlight, Windows installer
• Responsive admin portal with full CRUD for books, audio, users, and pricing
• Source code in a private repo, build scripts, and setup documentation
• Handoff call plus 30-day bug-fix window

Acceptance criteria
• Text and audio stay aligned within 0.5 s when paging, scrubbing, or changing playback speed
• Account creation, email verification, and password reset work end to end
• Offline reading/listening syncs progress on reconnect without breaking DRM
• Builds pass Play Store, App Store, and Microsoft Store compliance reviews

When you reply, tell me the stack you recommend (Flutter, React Native, Kotlin-Swift, or anything else that fits), a phased timeline, and links to similar work you have shipped. I am ready to move forward immediately.