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/prerm.sh

@@ -0,0 +1,9 @@
+#!/bin/sh
+set -e
+# dpkg passes "remove" here; rpm passes a numeric $1 (0 = last uninstall) - cover both.
+if { [ "$1" = "remove" ] || [ "$1" = "0" ]; } && [ -d /run/systemd/system ]; then
+  systemctl stop nasmon.service >/dev/null 2>&1 || true
+  systemctl disable nasmon.service >/dev/null 2>&1 || true
+  systemctl disable --now wsdd.service >/dev/null 2>&1 || true
+fi
+exit 0