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>

config/sudoers

@@ -1,4 +1,4 @@
-# VoxIP Kiosk OS: the web interface (user voxip) may run exactly one program
+# Daynivo Kiosk OS: the web interface (user voxip) may run exactly one program
 # as root: the restricted helper, which validates all of its input itself.
 Defaults:voxip !requiretty
 voxip ALL=(root) NOPASSWD: /usr/lib/voxip-kiosk/voxip-kiosk-helper