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.

src/main.js

@@ -155,6 +155,28 @@ ipcMain.handle('proxmox:connect', async (_e, { node, vmid }) => {
   }
 });
 
+// ---------- IPC: settings ----------
+
+ipcMain.handle('settings:platform', () => process.platform);
+
+ipcMain.handle('settings:getViewerPath', () => store.get('viewerPath', null));
+
+ipcMain.handle('settings:clearViewerPath', () => {
+  store.delete('viewerPath');
+});
+
+ipcMain.handle('settings:browseViewerPath', async () => {
+  const result = await dialog.showOpenDialog(mainWindow, {
+    title: 'remote-viewer.exe auswählen',
+    properties: ['openFile'],
+    filters: [{ name: 'remote-viewer', extensions: ['exe'] }],
+  });
+  if (result.canceled || result.filePaths.length === 0) return null;
+  const chosen = result.filePaths[0];
+  store.set('viewerPath', chosen);
+  return chosen;
+});
+
 // ---------- SPICE helpers ----------
 
 function buildVVFile(params, vmid) {
@@ -187,24 +209,55 @@ function buildVVFile(params, vmid) {
   return vvPath;
 }
 
+// VirtViewer's Windows installer names its folder after the bundled version
+// (e.g. "VirtViewer v11.0-256"), so a fixed path breaks on every version bump.
+// Scan the two Program Files dirs for any "VirtViewer*" folder instead.
+function findWindowsViewerCandidates() {
+  const roots = [
+    process.env['ProgramFiles'] || 'C:\\Program Files',
+    process.env['ProgramFiles(x86)'] || 'C:\\Program Files (x86)',
+  ];
+  const found = [];
+  for (const root of roots) {
+    let entries;
+    try {
+      entries = fs.readdirSync(root, { withFileTypes: true });
+    } catch {
+      continue;
+    }
+    for (const entry of entries) {
+      if (!entry.isDirectory() || !/^virtviewer/i.test(entry.name)) continue;
+      const exe = path.join(root, entry.name, 'bin', 'remote-viewer.exe');
+      if (fs.existsSync(exe)) found.push(exe);
+    }
+  }
+  return found;
+}
+
 function launchRemoteViewer(vvPath) {
-  const candidates =
-    process.platform === 'win32'
-      ? [
-          'remote-viewer',
-          path.join('C:', 'Program Files', 'VirtViewer', 'bin', 'remote-viewer.exe'),
-          path.join('C:', 'Program Files (x86)', 'VirtViewer', 'bin', 'remote-viewer.exe'),
-        ]
-      : ['remote-viewer', 'virt-viewer'];
+  let candidates;
+  if (process.platform === 'win32') {
+    const customPath = store.get('viewerPath', null);
+    candidates = [
+      ...(customPath ? [customPath] : []),
+      'remote-viewer',
+      ...findWindowsViewerCandidates(),
+    ];
+  } else {
+    candidates = ['remote-viewer', 'virt-viewer'];
+  }
 
   function tryNext(i) {
     if (i >= candidates.length) {
+      const hint =
+        process.platform === 'win32'
+          ? 'Windows: https://virt-manager.org/download/\n\n' +
+            'Falls VirtViewer an einem nicht-standardmäßigen Ort installiert ist, ' +
+            'trage den Pfad unter „Einstellungen → Viewer-Pfad" ein.'
+          : 'Linux:   sudo apt install virt-viewer';
       dialog.showErrorBox(
         'remote-viewer nicht gefunden',
-        'Bitte installiere virt-viewer:\n\n' +
-          '  Linux:   sudo apt install virt-viewer\n' +
-          '  Windows: https://virt-manager.org/download/\n\n' +
-          'Danach bitte erneut verbinden.'
+        'Bitte installiere virt-viewer:\n\n' + hint + '\n\nDanach bitte erneut verbinden.'
       );
       return;
     }