feat: auto-detect OS from description; expand OS_LIST to 51 distros

- Remove os field from Device API and form — OS is now detected
  automatically from name/description via detectOs() in brandIcons.js
- Expand OS_LIST from 20 to 51 entries covering all major distros
  (Debian/Ubuntu flavours, Red Hat, SUSE, Arch, BSD, security distros,
  Windows/macOS/iOS/Android, generic Linux/BSD catch-alls)
- Display detected OS icon in IpAddressing.vue description column
- Fix virt_type validator to normalise empty string to null

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

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "network-topology",
-  "version": "1.0.1",
+  "version": "1.1.0",
   "scripts": {
     "dev": "vite",
     "build": "vite build",