Full-Stack Developer Needed to Finish Existing React App, Build Backend & Add Live/Payment Features

I’m looking for an experienced full-stack/mobile app developer to help turn my existing frontend into a fully functional app. I created the current frontend/prototype in Google AI Studio. The source code is available and the frontend is already extensively designed, including the main app and admin panel screens. IMPORTANT: I am NOT looking to completely redesign or rebuild the frontend from scratch unless there is a specific technical reason a certain part cannot be used. I have put significant work into the current design and want the existing visual direction, screens, layouts, interactions, and overall experience preserved as much as possible. I need someone who is comfortable reviewing and improving an existing AI-generated React codebase, cleaning up problem areas, and connecting it to a real backend. Main work needed: FRONTEND CLEANUP - Review existing React frontend/source code - Fix mobile cropping and responsive layout issues - Fix design/layout bugs without unnecessarily changing the existing design - Improve code quality where necessary - Make interactions reliable across screens - Preserve the current UI/UX as closely as possible BACKEND - Build the backend from scratch - Database setup - User authentication/accounts - User profiles and account data - Connect all existing frontend screens to real data - Persistent app state - Admin/backend permissions MEDIA - Image uploading - Video uploading - Media storage - Video playback - User-generated content handling LIVE FEATURES - Live streaming/live transmission functionality - Viewer presence - Live interactions - Ability to send paid offerings/gifts during live sessions - Recommend an appropriate live streaming service/architecture OFFERINGS / COMMERCE The app allows users/facilitators to create and sell different types of offerings. I need: - Checkout/payment processing - Creator/facilitator earnings - Platform percentage calculations - Creator payout balances - Payment history - Refund/cancellation handling - Digital offering access - Live offering access/invites - Scheduled offering reservations - On-demand offering access - Physical product orders - Shipping information - Shipping/tracking status - Order fulfillment statuses - Inventory/capacity handling where applicable ADMIN PANEL The app does need a admin panel It should eventually support things such as: - User management - Reports/moderation - Offerings - Orders - Payments - Support cases - App management - Other administrative controls already represented in the frontend OTHER REQUIREMENTS - Secure backend architecture - Proper API integration - Error handling - Testing and bug fixing - Mobile responsiveness - Production-ready implementation - Help preparing the finished app for deployment/release I am open to your recommendation for the backend/database and services used for live streaming, media storage, payments, shipping/tracking, etc. When applying, please answer: 1. Are you comfortable working with an existing AI-generated React frontend instead of automatically rebuilding the entire UI? 2. Have you worked on apps with live streaming, media uploads, payments, creator payouts, marketplaces, or shipping/order tracking? 3. What backend stack would you recommend for this project? 4. Are there any parts of this scope you would need another specialist for? 5. Can you review the existing source code before giving a final estimate? 6. Please provide examples of similar apps/features you have built. I can provide the source-code ZIP, screenshots, screen recordings, and detailed explanations of the existing flows. Please do not apply if your standard approach is to discard an existing frontend and redesign the app from scratch. I’m specifically looking for someone who can preserve the existing product design while making it technically functional and production-ready.