I need a single Flutter code-base that runs smoothly on both iOS and Android. The primary flow is simple: I scan product barcodes at the counter, the app instantly pulls item details from stock, generates a bill, and the customer pays on the spot through integrated UPI or by scanning a QR the app creates. As soon as the payment is confirmed, the sale is logged, inventory is updated, and a receipt is stored for download. Behind the scenes, an admin area must give me full stock control. Every time quantities dip below a threshold an inventory alert should pop up, and I want a clean supplier section where I can record purchase orders, contact details, and settlement status. From both the sales side and the inventory side I’ll need quick “one-tap” report generation so I can export daily, weekly, or custom-range PDFs/CSVs of transactions and stock levels. Clean, modular code is a must. Follow standard Flutter best practices (state management with Provider, Riverpod, BLoC—or whichever pattern you favour—so long as it’s consistent and well-documented). Comment critical sections, keep widgets reusable, and structure folders so future contributors can onboard quickly. Deliverables • Complete Flutter source code with clear folder structure • iOS and Android release builds ready for store submission or direct install • Simple setup guide covering environment, build commands, and how to link the UPI/QR payment gateway you choose • Brief user manual that shows barcode scan → bill → payment → report workflow • Basic test data so I can demonstrate inventory alerts, supplier records, and report downloads right away Acceptance criteria 1. Barcode scan adds the item to the cart in under two seconds. 2. Bill generation produces a sharable PDF or thermal-printer ready receipt. 3. UPI intent and QR payments update order status automatically on success/failure callbacks. 4. Inventory alert triggers when stock ≤ user-defined threshold. 5. All reports export correctly in both PDF and CSV formats. Once these points check out and the documentation is clear, the project is done.