feat: expand discovery with systemd services, LXC/VMs, SSH terminal, and filebrowser

- Add systemd service discovery to backend
- Add Proxmox LXC/VM detection
- Add hostType field to config for better host categorization
- Fix SSH trust between hosts (ubuntu/grizzley -> truenas/proxmox)
- Add SSH terminal support via xterm.js
- Add filebrowser for browsing host filesystems
- Update frontend types and components for new node types

package.json

@@ -15,6 +15,8 @@
     "@types/cors": "^2.8.19",
     "@types/dagre": "^0.7.53",
     "@types/express": "^5.0.6",
+    "@xterm/addon-fit": "^0.11.0",
+    "@xterm/xterm": "^6.0.0",
     "@xyflow/react": "^12.4.4",
     "cors": "^2.8.6",
     "dagre": "^0.8.5",