You are a senior full-stack engineer. Build a mobile-first live auction marketplace app (similar to Whatnot) focused on thrift fashion in India. Tech stack: - Frontend: React Native (Expo) - Backend: Node.js + Express - Database: MongoDB - Realtime: Socket.io - Payments: Razorpay (UPI support) Core Features: 1. Authentication: - User signup/login (email + OTP optional) - Separate roles: Buyer and Seller 2. Seller Features: - Create live auction session - Add products before going live (title, price, images, size, condition) - Start live stream (mock video or placeholder for now) - Start auction for each item with: - Base price - Timer (30–60 seconds) - See live bids in real time 3. Buyer Features: - Join live sessions - View products in auction - Place bids in real-time - See countdown timer - “Winning” indicator if highest bidder 4. Auction Logic: - Real-time bidding using Socket.io - Minimum bid increment (₹10 or ₹50) - Auto-update highest bidder - Auction ends when timer hits zero - Declare winner 5. Checkout: - Winner gets “Buy Now” screen - Integrate Razorpay test mode - Simple order confirmation screen 6. UI/UX: - Clean, modern UI (dark + hype theme) - Instagram Live + Whatnot inspired - Include: - Live chat - Floating hearts/reactions - Countdown timer UI 7. Admin (basic): - View users - View transactions Folder structure: - Separate frontend and backend clearly Deliverables: - Complete working MVP - Clear setup instructions - Dummy data for testing Important: - Focus on working prototype, not perfection - Mock video streaming if needed (don’t overcomplicate) - Prioritize real-time bidding functionality