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/renderer/vms.html

@@ -14,6 +14,7 @@
     <div class="page-header">
       <h2>Virtuelle Maschinen</h2>
       <div class="header-actions">
+        <button id="settingsBtn" class="btn-secondary hidden" title="Viewer-Pfad einstellen">⚙ Einstellungen</button>
         <button id="refreshBtn" class="btn-secondary" title="Liste aktualisieren">↻ Aktualisieren</button>
         <button id="logoutBtn" class="btn-secondary">Abmelden</button>
       </div>
@@ -42,6 +43,26 @@
 
   </div>
 
+  <!-- Settings modal (Windows only — VirtViewer's install folder name changes per version) -->
+  <div id="settingsOverlay" class="modal-overlay hidden">
+    <div class="modal-card">
+      <h3>Viewer-Pfad</h3>
+      <p class="hint">
+        Wird VirtViewer (remote-viewer.exe) nicht automatisch gefunden, kannst du hier
+        den Pfad zur .exe manuell festlegen.
+      </p>
+      <div class="field">
+        <label>Aktueller Pfad</label>
+        <div id="viewerPathDisplay" class="path-display">automatisch erkannt</div>
+      </div>
+      <div class="modal-actions">
+        <button id="browseViewerBtn" class="btn-secondary">Durchsuchen…</button>
+        <button id="resetViewerBtn" class="btn-secondary">Zurücksetzen</button>
+        <button id="closeSettingsBtn" class="btn-primary modal-close">Schließen</button>
+      </div>
+    </div>
+  </div>
+
   <script src="vms.js"></script>
 </body>
 </html>