ci: Integrate IaC Static Analysis and Security Scanning

[carlagesa]

To "shift-left" on security and code quality, we need to integrate automated scanning tools into our CI/CD pipeline. This will help us catch potential misconfigurations, security vulnerabilities, and non-compliant code before it gets deployed. We should add steps to our pipeline for linting (tflint) and security scanning (tfsec or checkov).
Acceptance Criteria:

• The CI/CD pipeline configuration is updated with a new stage for IaC scanning.
• tflint is added to check for Terraform best practices and potential errors.
• tfsec (or a similar tool) is added to scan for security vulnerabilities.
• The pipeline fails if the scanners detect issues of a certain severity (e.g., HIGH).