test: add native Terraform validation tests

[afaryy]

Summary

• add backend-free native Terraform tests for implemented Terraform roots
• run terraform test after terraform validate for detected changed roots
• document that Terraform tests do not report coverage to SonarQube
• update backlog status for completed P6 migration and deployment work

Validation

• terraform fmt
• terraform init -backend=false
• terraform validate
• terraform test
• TFLint
• workflow YAML parse
• Markdown local link checks

Scope

• no Terraform resource behavior changes
• no CloudFormation changes
• no application code changes
• no Dockerfile changes
• no AWS resources changed

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud