Support multiple standalone Proxmox hosts with shared credentials

Comma-separated host list logs into every host, merges VM lists tagged
by origin host, and routes SPICE connections to the right one. Also
adds a username format hint (user@realm) on the login form.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "proxmox-spice-client",
-  "version": "1.0.1",
+  "version": "1.0.2",
   "description": "VDI SPICE Client f\u00fcr Proxmox",
   "main": "src/main.js",
   "scripts": {