Rename the visible VoxIP texts to Daynivo

Product name (Daynivo Kiosk OS), default device name, kiosk screens,
service descriptions, installer output and docs. Internal names
(voxip-kiosk-*, /etc/voxip-kiosk, user voxip, VOXIP_* variables) stay.
An update renames a device still called "VoxIP Kiosk" to the new default.

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

update.sh

@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 #
-# Update VoxIP Kiosk OS from this checkout (or an extracted release).
+# Update Daynivo Kiosk OS from this checkout (or an extracted release).
 #
 #   sudo ./update.sh            # git pull --ff-only, back up config, install --upgrade
 #   sudo ./update.sh --no-pull  # install the code as it is in this directory