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>

.gitattributes

@@ -0,0 +1,15 @@
+# Files that end up on the Linux server must keep LF endings
+*.sh    text eol=lf
+*.yml   text eol=lf
+*.json  text eol=lf
+.env*   text eol=lf
+*.ps1   text eol=crlf
+*.go     text eol=lf
+*.yaml   text eol=lf
+*.html   text eol=lf
+*.css    text eol=lf
+*.js     text eol=lf
+*.md     text eol=lf
+*.service text eol=lf
+go.mod  text eol=lf
+go.sum  text eol=lf