Document production settings (DEBUG, SECRET_KEY, ALLOWED_HOSTS)

[arunb-lab]

Add documentation for configuring the project safely for production/deployment.

Suggested approach

• Explain reading SECRET_KEY from an environment variable instead of hardcoding it
• Document setting DEBUG = False in production and configuring ALLOWED_HOSTS
• Mention serving static files and using a production-ready database
• Add a short "Deployment" section to the README and an example .env

This helps learners move from local development to a real deployment safely.