fix: close OVA build gaps — 24.04, overlay copy, full compose stack

- Replace ubuntu-26.04 (unreleased) with ubuntu-24.04 LTS throughout
- Add file provisioner to Packer HCL to copy overlays/ into VM before
  provisioning (fixes missing zroc-setup binary in 03-setup-wizard.sh)
- Rebuild root docker-compose.yaml: full stack with env vars — Caddy,
  zroc-ui, Authentik (server + worker + postgres + redis), Prometheus,
  Grafana, Zerto exporter, Watchtower; no hardcoded credentials
- Add caddy/Caddyfile to repo root for reverse proxy / TLS
- Update 02-zroc.sh to pre-pull all service images during OVA build
- Update GitHub Actions workflow to reference ubuntu-2404.pkr.hcl

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

zroc-ova/scripts/03-setup-wizard.sh

@@ -3,7 +3,10 @@
 set -euo pipefail
 echo "==> [03-setup-wizard] Installing setup wizard"
 
-install -m 0755 /tmp/zroc-setup /usr/local/bin/zroc-setup
+# The Packer file provisioner copies overlays/ to /tmp/overlays/
+# Mirror the full directory tree into place
+cp -r /tmp/overlays/usr /
+chmod 0755 /usr/local/bin/zroc-setup
 
 cat > /etc/systemd/system/zroc-firstboot.service << 'EOF'
 [Unit]