- Add new load_balancer module with ALB, target group, and listeners
- Configure HTTPS listener with optional ACM certificate support
- Add HTTP to HTTPS redirect when certificate is provided
- Update security groups to allow ALB → ECS traffic on port 8000
- Integrate ALB with ECS service using dynamic load_balancer block
- Add ALB outputs (backend URLs and DNS name)
- Update documentation with backend access instructions
- Update cost estimation to include ALB (~$16-25/month)

The backend API is now publicly accessible via the ALB DNS name.
Health check grace period increased to 120s for ALB integration.