Introduce a complete Kiwix LXC installer: ct/kiwix.sh (container template) and install/kiwix-install.sh (in-container install). The installer installs kiwix-tools from the Kiwix PPA, creates a systemd kiwix-serve service to serve /data/*.zim on port 8080, records the package version in /root/.kiwix, and includes an update_script to upgrade kiwix-tools. The container template validates a provided ZIM_DATA directory, configures a bind mount (using ID-mapped mounts if available), sets container options, and prints the service URL. Also add json/kiwix.json catalog metadata with usage notes (including ZIM_DATA usage and file permission guidance).
