fix: optimize shell scripts and add distrobox-plus attribution

- Add timeout to sudo test to prevent hanging (distrobox-export.sh)
- Fix flatpak path with missing trailing slash (distrobox-export.sh)
- Use dynamic path lookup for distrobox-host-exec instead of hardcoded paths
- Change version to use DISTROBOX_VERSION env variable with fallback
- Update header comments to reference distrobox-plus project

Author: xz-dev

pyproject.toml

@@ -36,7 +36,6 @@ Issues = "https://github.com/xz-dev/distrobox-plus/issues"
 
 [project.scripts]
 distrobox-plus = "distrobox_plus:main"
-distrobox-export = "distrobox_plus.commands.export:run"
 distrobox-generate-entry = "distrobox_plus.commands.generate_entry:run"
 
 [build-system]