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

server/types.ts

@@ -17,6 +17,8 @@ export interface HostConfig {
   sshKeyPath?: string;
   /** Optional SSH port (defaults to 22) */
   sshPort?: number;
+  /** Host type: proxmox, truenas, docker-host, etc */
+  hostType?: string;
 }
 
 export interface DiscoveryResponse {
@@ -26,6 +28,8 @@ export interface DiscoveryResponse {
     ip: string;
     online: boolean;
     containers?: string[];
+    services?: string[];
+    vms?: Array<{ id: string; name: string; status: string; type: 'lxc' | 'qemu' }>;
     error?: string;
   }>;
   /** Timestamp of discovery run */