Add support for an API proxy

See merge request !311

Add an indicator of whether the CPU has been throtting (usually due
to thermal constraints) to the host dashboard, overlaid on top of
the CPU usage graph as a red line.

By embedding the bits in the file name we can make it so NGINX
gets automatically restarted if dhparam_bits changes.

These are associated with xfs filesystems.

This reverts commit 47dc8a09.

Trying to address trixie test flakiness.

This removes some flakiness with newer Ansible and Debian releases,
at the expense of CI test speed.

Prevent alerting when SMART tests haven't run yet.

Since we've added SMART alerts, we should install smartd as well.
As most testing happens in VMs, the SMART functionality will only
be enabled when testing==False.

Since current Debian oldstable we are just using the Debian packages.

This reverts commit 9dab0907.

There's no longer a "ntp" system user?

Try a recent Ansible version to deal with targets having Python 3.12.

Require more ICMP probes to fail before the alert triggers.

Expose test artifacts to the Gitlab CI interface

See merge request !310

The artifacts are saved outside of the test container and retrieved
to the CI runner.

Tune nginx proxy_cache_path parameters

See merge request !309

Introduce the 'nginx_cache_params_custom' configuration variable.