feat: Add Infrastructure as Code Fundamentals blog post (#969)

* feat: Add comprehensive Infrastructure as Code fundamentals blog post

Closes #964

- Created detailed IaC fundamentals guide (851 lines)
- Covers: What IaC is, why it matters, declarative vs imperative
- Explains popular tools: Terraform, CloudFormation, Pulumi, Ansible
- Includes essential concepts: state, modules, idempotency, drift
- Details best practices for version control, security, environments
- Provides step-by-step getting started tutorial with Terraform
- Lists common pitfalls and how to avoid them
- Includes learning path (beginner to advanced)
- Links to related exercises (DigitalOcean Droplet with Terraform)
- Matches tone and depth of existing beginner guides
- All 4,561 tests passing

* fix: Update technical accuracy in IaC post

- Use aws_ami data source instead of hardcoded AMI ID
- Add missing egress rule to security group example
- Update Terraform version from 1.7.0 to 1.10.5
- Fix Terraform docs URL to new HashiCorp developer site

* fix: Update title to reflect beginner focus, fix diagrams, add OG images

Author: bobbyonmagic