Shelly 3.1 adds native Arch package builder with full PKGBUILD support

Shelly 3.1 brings a native Arch Linux package builder, integrating the entire build pipeline and removing reliance on makepkg for default AUR workflows.

The update supports the complete PKGBUILD format, ensuring compatibility with standard Arch packaging practices.

Security enhancements include interactive package review, file integrity checks, and optional Landlock sandboxing for safe builds.