Fix VirtViewer detection on Windows + manual path override

VirtViewer's installer folder name includes the version number
(e.g. "VirtViewer v11.0-256"), so the previous hardcoded path never
matched a real install. Now scans Program Files for any VirtViewer*
folder, and adds a Settings dialog (Windows only) to pick the
remote-viewer.exe path manually as a fallback.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "proxmox-spice-client",
-  "version": "1.0.0",
+  "version": "1.0.1",
   "description": "VDI SPICE Client f\u00fcr Proxmox",
   "main": "src/main.js",
   "scripts": {