Rename the web interface to Daynivo Kiosk Manager with the Daynivo logo

The Daynivo mark sits on a small white tile in the navy bar, where its
navy parts would otherwise disappear; the favicon is Daynivo's too.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

systemd/voxip-kiosk-manager.service

@@ -1,5 +1,5 @@
 [Unit]
-Description=VoxIP Kiosk Manager (webbeheer)
+Description=Daynivo Kiosk Manager (webbeheer)
 Documentation=file:///usr/share/doc/voxip-kiosk/README.md
 After=network.target voxip-boot-import.service
 StartLimitIntervalSec=300