v0.3.0

FreeBSD inventory support + VirtualBox serial parity. A single codebase now
builds for Linux, Windows and FreeBSD. Validated end-to-end on FreeBSD 14.1 against
a real GLPI 10 (native JSON schema-valid, asset created), and the Linux build
cross-checked on Debian 12 against the official glpi-agent (softwares 455/455).

✨ New Features

• feat(freebsd): FreeBSD inventory support — go-glpi-agent collects the same
  categories on FreeBSD via gopsutil plus native sources: kenv smbios.*
  (BIOS/board/chassis/UUID), pkg query (software), geom/camcontrol (disks),
  sysctl (CPU/OS), /var/db/zoneinfo (timezone) and usbconfig (USB).
• feat(freebsd): FreeBSD distribution — make build-freebsd/package-freebsd
  produce a .tar.gz (binary + agent.cfg + rc.d service + INSTALL.md);
  release.yml publishes it.

🔧 Improvements

• fix(bios): on VirtualBox VMs, where the DMI/SMBIOS serial is 0, fall back to the
  system UUID as the serial (matching glpi-agent's Generic/Dmidecode/Bios.pm), so
  the host gets a stable identity in GLPI instead of an empty serial. Applies to
  Linux, Windows and FreeBSD.
• refactor: per-OS registration extended with register_freebsd.go; cross-platform
  generic timezone gains a FreeBSD source (/var/db/zoneinfo).
• ci: go.yml adds a GOOS=freebsd build/vet check.

📚 Documentation

• docs: README "FreeBSD" section + a FreeBSD column in the per-OS collector table;
  AGENTS.md per-OS layout; test/vagrant-freebsd/ end-to-end validation comparing
  against the official p5-FusionInventory-Agent.

Full Changelog: v0.2.0...v0.3.0