feat: Installer mit automatischer VirtViewer-Abhängigkeit

- Windows NSIS: lädt VirtViewer MSI herunter und installiert es
  während der App-Installation (via PowerShell + msiexec)
- Linux .deb: Depends: virt-viewer — apt zieht es automatisch rein
- Linux AppImage: Startup-Check mit pkexec-Dialog falls virt-viewer fehlt
- BUILD.md aktualisiert: Installer-Verhalten dokumentiert

src/main.js

@@ -2,7 +2,7 @@ const { app, BrowserWindow, ipcMain, dialog } = require('electron');
 const path = require('path');
 const fs = require('fs');
 const os = require('os');
-const { spawn } = require('child_process');
+const { spawn, spawnSync } = require('child_process');
 const Store = require('electron-store');
 const ProxmoxClient = require('./proxmox');
 
@@ -38,6 +38,7 @@ function createWindow(file, width, height, resizable = false) {
 
 app.whenReady().then(() => {
   createWindow('login.html', 460, 500, false);
+  checkDependencies();
   app.on('activate', () => {
     if (!mainWindow) createWindow('login.html', 460, 500, false);
   });
@@ -47,6 +48,63 @@ app.on('window-all-closed', () => {
   if (process.platform !== 'darwin') app.quit();
 });
 
+// ---------- Dependency check (AppImage / manual install on Linux) ----------
+
+function checkDependencies() {
+  // On Windows the NSIS installer handles virt-viewer — no runtime check needed.
+  // On Linux (AppImage or manual install) we check here so the user knows before
+  // trying to connect for the first time.
+  if (process.platform !== 'linux') return;
+
+  const candidates = ['remote-viewer', 'virt-viewer'];
+  const found = candidates.some(bin => {
+    const r = spawnSync('which', [bin], { encoding: 'utf8' });
+    return r.status === 0;
+  });
+
+  if (!found) {
+    setImmediate(() => {
+      const choice = dialog.showMessageBoxSync(mainWindow, {
+        type: 'warning',
+        title: 'Abhängigkeit fehlt',
+        message: 'VirtViewer nicht gefunden',
+        detail:
+          'VirtViewer (remote-viewer) wird für SPICE-Verbindungen benötigt und ist auf diesem System nicht installiert.\n\n' +
+          'Installieren mit:\n  sudo apt install virt-viewer\n\n' +
+          'Soll die App versuchen, VirtViewer jetzt automatisch zu installieren?',
+        buttons: ['Jetzt installieren', 'Später (manuell)'],
+        defaultId: 0,
+        cancelId: 1,
+      });
+
+      if (choice === 0) {
+        const installer = spawn(
+          'pkexec',
+          ['apt', 'install', '-y', 'virt-viewer'],
+          { detached: false, stdio: 'ignore' }
+        );
+        installer.on('close', code => {
+          if (code === 0) {
+            dialog.showMessageBox(mainWindow, {
+              type: 'info',
+              title: 'VirtViewer installiert',
+              message: 'VirtViewer wurde erfolgreich installiert.',
+              buttons: ['OK'],
+            });
+          } else {
+            dialog.showMessageBox(mainWindow, {
+              type: 'error',
+              title: 'Installation fehlgeschlagen',
+              message: `Installation schlug fehl (Code ${code}).\nBitte manuell ausführen:\n  sudo apt install virt-viewer`,
+              buttons: ['OK'],
+            });
+          }
+        });
+      }
+    });
+  }
+}
+
 // ---------- IPC: credentials ----------
 
 ipcMain.handle('credentials:load', () => store.get('credentials', null));
@@ -65,7 +123,6 @@ ipcMain.handle('proxmox:login', async (_e, { host, username, password }) => {
   try {
     client = new ProxmoxClient(host);
     await client.login(username, password);
-    // Switch to VM list view
     createWindow('vms.html', 680, 520, true);
     return { success: true };
   } catch (err) {
@@ -103,7 +160,6 @@ ipcMain.handle('proxmox:connect', async (_e, { node, vmid }) => {
 function buildVVFile(params, vmid) {
   const lines = ['[virt-viewer]', `type=${params.type || 'spice'}`];
 
-  // Proxmox spiceproxy returns 'proxy' as the SPICE host
   const host = params.proxy || params.host || client.host.split(':')[0];
   lines.push(`host=${host}`);
 
@@ -111,7 +167,6 @@ function buildVVFile(params, vmid) {
   if (params.port) lines.push(`port=${params.port}`);
   if (params.password) lines.push(`password=${params.password}`);
 
-  // Write CA cert to temp file if provided
   if (params.ca) {
     const caPath = path.join(os.tmpdir(), 'proxmox-spice-ca.pem');
     fs.writeFileSync(caPath, params.ca);
@@ -119,14 +174,13 @@ function buildVVFile(params, vmid) {
   }
   if (params['host-subject']) lines.push(`host-subject=${params['host-subject']}`);
 
-  // UX + USB
   lines.push('fullscreen=0');
   lines.push('title=%d — SPICE');
-  lines.push('delete-this-file=1'); // remote-viewer deletes the file after reading (hides password)
+  lines.push('delete-this-file=1');
   lines.push('toggle-fullscreen=shift+f11');
   lines.push('release-cursor=shift+f12');
   lines.push('secure-attention=ctrl+alt+end');
-  lines.push('usb-filter=-1,-1,-1,-1,0'); // allow all USB devices
+  lines.push('usb-filter=-1,-1,-1,-1,0');
 
   const vvPath = path.join(os.tmpdir(), `spice-${vmid}-${Date.now()}.vv`);
   fs.writeFileSync(vvPath, lines.join('\n') + '\n', { mode: 0o600 });
@@ -143,8 +197,6 @@ function launchRemoteViewer(vvPath) {
         ]
       : ['remote-viewer', 'virt-viewer'];
 
-  let launched = false;
-
   function tryNext(i) {
     if (i >= candidates.length) {
       dialog.showErrorBox(
@@ -158,7 +210,7 @@ function launchRemoteViewer(vvPath) {
     }
     const child = spawn(candidates[i], [vvPath], { detached: true, stdio: 'ignore' });
     child.on('error', () => tryNext(i + 1));
-    child.on('spawn', () => { launched = true; });
+    child.on('spawn', () => { });
     child.unref();
   }