Add unit files to manage services with systemd

Description

Now that we're on EL9, I think we can simplify how we manage calibration services by using user-level systemd. This adds unit files for the 3 services. It will also need changes to the deployment machinery to install these files & start the services.

How Has This Been Tested?

TBD

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the code style of this project.

Reviewers

@roscar @schmidtp

webservice/systemd/cal-job-monitor.service

+[Unit]
+Description=XFEL offline calibration Slurm job monitor
+
+[Service]
+Type=exec
+WorkingDirectory=%h/deployments/development/git.xfel.eu/detectors/pycalibration/current/
+ExecStart=%h/deployments/development/git.xfel.eu/detectors/pycalibration/current/.venv/bin/python -m webservice.job_monitor --log-level DEBUG
+Restart=on-failure
+
+[Install]
+WantedBy=default.target