feat!: stabilize AWS Backup module v1

[caiohasouza]

Summary

• Modernize the migrated terraform-aws-backup module using the terraform-aws-cloud-custodian repository template.
• Raise Terraform and AWS provider constraints according to the approved plan.
• Preserve all 16 public variables and 5 outputs.
• Add CI, Semantic Release, pre-commit, generated documentation and a complete example.
• Fix evaluated legacy syntax and guard selections and notifications when their dependent resources are disabled.

Baseline

• GitLab branch: master
• Baseline SHA: 31447b04846cf546c3084d932ce4cc8551cc262f
• Baseline tag: v0.1.0

Validation

• terraform fmt -check -recursive
• terraform init -backend=false
• terraform validate
• pre-commit run --all-files
• tflint --init and TFLint checks
• Trivy config scan, with the pre-existing wildcard IAM finding documented in migration evidence
• Terraform test fixture with disabled, named-selection and two-selection cases; plans show zero destroys

BREAKING CHANGE: stabilize the public v1 module contract without removing variables or outputs.

[ganex-gh-actions-release]

This PR is included in version 1.0.0 🎉