Add a Debian package and bash completion

make deb builds dist/jarl_<version>_<arch>.deb with dpkg-deb alone (no
root), for the host or another architecture (DEB_ARCH=arm64). The package
creates the jarl user and directories and an example jarl.yaml on the
first install, restarts a running jarld on upgrades, never touches
/etc/jarl/jarl.yaml, stops jarld on removal, and keeps Jarl's data even
on purge.

make install and the package install bash completion for jarl and jarld.
Besides commands and flags it completes server and group names from the
CLI configuration, zone, view, ACL, TSIG key and user names from the
server, and record types. make dist includes the completion scripts.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -64,9 +64,7 @@ On a Debian/Ubuntu BIND 9.20 server ([install.md](docs/install.md) has the
 details):
 
 ```sh
-make && sudo make install
-sudo systemd-sysusers jarl.conf && sudo systemd-tmpfiles --create jarl.conf
-sudo chgrp jarl /etc/jarl/jarl.yaml
+make deb && sudo apt install ./dist/jarl_*.deb   # or: make && sudo make install, see install.md
 sudo -u jarl jarld init --token            # first admin + a CLI token
 sudo -u jarl jarld import                  # read the current named.conf and zones
 sudo jarld adopt                           # switch named over (keeps a backup, rolls back on failure)