Add pacman/Arch Linux package detection support for Linux antivirus check

The Linux antivirus check currently relies on package-inventory tables (deb_packages, rpm_packages, etc. via osquery), which have no equivalent for pacman-based distributions (Arch Linux, Manjaro, EndeavourOS, Omarchy, and others). As a result, any antivirus solution installed via pacman — including ClamAV, which is on your supported list — can never be detected, regardless of whether it's correctly installed and running.

We verified this on an Omarchy (Arch-based) device: ClamAV was installed, running, and actively detecting malware (confirmed via EICAR test), and the underlying osquery processes table showed clamd/freshclam running correctly — but no pacman_packages table exists for the compliance check to query against, so the device was flagged as having no antivirus.