Add Terraform Testing for Guides to CI Pipeline

[tessmichi]

📝 Description

Ensure Terraform code quality by adding automated testing:

• Run terraform fmt -check for formatting validation
• Execute terraform validate for configuration validation
• Run Terraform test files (*.tftest.hcl) in CI pipeline
• Implement terraform plan with cost estimation where possible
• Add security scanning for Terraform configurations (e.g., tfsec or checkov)

🔰 Code of Conduct

• I agree to follow this project's Code of Conduct.