Initial import: nasmon health monitor, split out of home_nas

Go service (nasmon/) plus nfpm packaging (packaging/), carried over from
the home_nas monorepo. Adds rpm packaging alongside the existing deb
build (Fedora/RHEL/Rocky dependency names via nfpm overrides, per-format
systemd unit path, dpkg+rpm-compatible maintainer scripts) and a Gitea
Actions workflow that builds both formats on every push.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

packaging/nasmon.service

@@ -0,0 +1,27 @@
+[Unit]
+Description=nasmon - NAS health monitor (SMART/ZFS dashboard and alerts)
+Documentation=file:///usr/share/doc/nasmon/README.md
+After=network-online.target zfs.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+# smartctl and zpool need root
+User=root
+ExecStart=/usr/bin/nasmon -listen :8090 -config /etc/nasmon/config.json -data /var/lib/nasmon
+Restart=on-failure
+RestartSec=5s
+
+# hardening
+NoNewPrivileges=yes
+PrivateTmp=yes
+ProtectSystem=strict
+ProtectHome=yes
+ReadWritePaths=/var/lib/nasmon /etc/nasmon
+ProtectKernelTunables=yes
+ProtectControlGroups=yes
+RestrictSUIDSGID=yes
+LockPersonality=yes
+
+[Install]
+WantedBy=multi-user.target