[docker] Add Trivy security scanning and enhance container security

[Copilot]

This PR enhances the Docker optimization work from #58 by adding comprehensive security scanning and build improvements.

Security Enhancements

Trivy Integration:

• Added Trivy vulnerability scanning to CI pipeline with SARIF output uploaded to GitHub Security tab
• New make docker-scan target for local security scanning with automatic installation guidance
• Scanning focuses on HIGH and CRITICAL vulnerabilities for actionable security insights

Build Security:

• Enhanced Go build flags with -s -extldflags '-static' for static linking and symbol stripping
• Updated Alpine base image from 3.18 to 3.20 for latest security patches
• Improved binary security through additional compiler flags

Example Usage

# Local security scanning
make docker-scan

# CI automatically scans on PR/push with results in Security tab
# Enhanced build produces smaller, more secure binaries

Testing:

• All existing tests pass with no regressions
• Added dedicated Docker security tests to validate enhancements
• Makefile targets properly validated

The Docker optimization from #58 provided an excellent foundation with multi-stage builds, non-root execution, health checks, and proper volumes. This PR adds the missing security scanning layer and hardens the build process further.

Fixes #47.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• invalid-host
  • Triggering command: /tmp/go-build544346517/b342/admin.test -test.testlogfile=/tmp/go-build544346517/b342/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.parallel=8 -test.v=true (dns block)
• invalid-host-that-does-not-exist
  • Triggering command: /tmp/go-build544346517/b342/admin.test -test.testlogfile=/tmp/go-build544346517/b342/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.parallel=8 -test.v=true (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[mfittko]

defered