Add Debian packaging and update Forgejo workflow

- Add complete Debian packaging configuration (debian/ directory)
- Create build-deb.sh script for building packages
- Update Forgejo workflow to build and upload .deb artifacts
- Add comprehensive version naming for both binary and Debian artifacts
- Update .gitignore to exclude build artifacts and packaging files
- Add PACKAGING.md documentation
- Add test-deb.sh for testing package installation

debian/control

@@ -11,6 +11,7 @@ Vcs-Browser: https://git.raines.xyz/robojerk/deb-bootupd
 Package: deb-bootupd
 Architecture: any
 Depends: ${shlibs:Depends}, ${misc:Depends}, efibootmgr, grub-common
+Recommends: ostree
 Description: Debian-compatible bootloader updater for immutable systems
  deb-bootupd is a sophisticated, production-ready Rust-based CLI tool that
  provides cross-distribution, OS update system agnostic bootloader management