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>

src/voxip_kiosk/web/templates/base.html

@@ -58,7 +58,7 @@
 
   <footer class="footer">
     <span>{{ device_name }} · {{ hostname }}</span>
-    <span>VoxIP Kiosk OS {{ version }}</span>
+    <span>Daynivo Kiosk OS {{ version }}</span>
   </footer>
 
   <dialog id="confirm-dialog" class="dialog">