Fix cert export: use PFX instead of PEM for .NET Framework compat

ExportPkcs8PrivateKey() is only available in .NET Core 3.0+
but Windows PowerShell 5.1 uses .NET Framework 4.x.
Switch to PFX export which works on all Windows versions.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

installer/local-server.js

@@ -102,18 +102,20 @@ function handleRequest(req, res) {
 }
 
 // Zertifikate laden und HTTPS-Server starten
-const certFile = path.join(CERT_DIR, "localhost.crt");
-const keyFile = path.join(CERT_DIR, "localhost.key");
+const pfxFile = path.join(CERT_DIR, "localhost.pfx");
+const pfxPasswordFile = path.join(CERT_DIR, "pfx-password.txt");
 
-if (!fs.existsSync(certFile) || !fs.existsSync(keyFile)) {
+if (!fs.existsSync(pfxFile) || !fs.existsSync(pfxPasswordFile)) {
   console.error("Zertifikate nicht gefunden in:", CERT_DIR);
-  console.error("Bitte zuerst setup.ps1 ausführen.");
+  console.error("Bitte zuerst setup.ps1 ausfuehren.");
   process.exit(1);
 }
 
+const pfxPassword = fs.readFileSync(pfxPasswordFile, "utf-8").trim();
+
 const serverOptions = {
-  cert: fs.readFileSync(certFile),
-  key: fs.readFileSync(keyFile),
+  pfx: fs.readFileSync(pfxFile),
+  passphrase: pfxPassword,
 };
 
 const server = https.createServer(serverOptions, handleRequest);