You are a Python web developer. Build an e-commerce website using Django. The site should: 1) Have product catalog with categories, 2) User registration and login, 3) Shopping cart functionality, 4) Checkout process with order placement, 5) Payment integration (Stripe or PayPal), 6) Order history for users, 7) Admin panel for managing products and orders, 8) Responsive design. Provide the full code and a requirements.txt.