v0.4.0

This release modernizes the entire project infrastructure while preserving all functionality.

• Start using Go Modules, removed vendor directory.
• Replaced Travis CI with modern with Github Actions.
• Go 1.25.
• Multi-platform builds: Linux, macOS, Windows (amd64/arm64).
• Security scanning: GoSec + govulncheck integration.
• Automated testing: Cross-platform test matrix.
• Multiple code-quality related changes.