Add close button to print QR page; fix QR generation to use file_put_contents

templates/print_qr.twig

@@ -26,7 +26,14 @@
             {% endif %}
         </div>
     </div>
-    <script>window.print();</script>
+    <div style="text-align: center; margin-top: 20px;">
+        <button onclick="window.close()">Sluit</button>
+    </div>
+    <script>
+        window.print();
+        // Optionally, close after print, but browser support varies
+        // window.onafterprint = function() { window.close(); };
+    </script>
 </body>
 </html>
 {% endautoescape %}