Environment Variables Best Practices

# Environment Variables Guide

## Setup
- Use .env files
- Never commit secrets
- Use .env.example template
- Document all variables

## Next.js Environment Variables
- Use NEXT_PUBLIC_ prefix
- Server vs client variables
- Load from .env.local
- Use environment-specific files

## Security
- Rotate secrets regularly
- Use secret managers
- Validate required variables
- Don't log sensitive data

## Best Practices
- Type environment variables
- Validate on startup
- Use different values per environment
- Document usage