Add the jarld.service alias for jarl.service

systemctl restart/status jarld now work too. The package relinks a unit
enabled by an older version on upgrade, so the alias appears without
re-enabling; make uninstall removes the link.

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

docs/install.md

@@ -317,6 +317,10 @@ systemctl status jarl
 journalctl -u jarl -f
 ```
 
+The unit also answers to `jarld` (`Alias=jarld.service`), so
+`systemctl restart jarld` and `journalctl -u jarl` work alike once it
+is enabled.
+
 Open `https://<management-address>:8053/` and log in as `admin`.
 
 ## 9. Set up the CLI