Enhancement: Automate GitHub Actions dependency updates

[coderabbitai]

Context

Currently, the action uses semantic version tags for external GitHub Actions dependencies (e.g., aquasecurity/trivy-action@0.33.1, docker/build-push-action@v5).

Enhancement Goal

Explore and implement automated tooling to keep GitHub Actions dependencies up to date, considering:

• Dependabot: Native GitHub solution for dependency updates
• Renovate: Third-party option with advanced configuration capabilities

Both tools can be configured to:

• Automatically detect outdated action versions
• Open pull requests with updates
• Optionally pin to commit SHAs for enhanced supply-chain security

Background

This enhancement was identified during security scanning feature development to improve long-term maintainability and security posture of the action's dependencies.

References

• Related PR: Add built-in Trivy vulnerability scanning with GitHub Security integration #7
• Discussion: Add built-in Trivy vulnerability scanning with GitHub Security integration #7 (comment)
• Requested by: @warengonzaga

Priority

Low - future enhancement; timing to be determined by maintainer.