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>

www/offline.html

@@ -24,7 +24,7 @@
     </main>
     <footer class="bottom">
       <span id="admin"></span>
-      <span>VoxIP Kiosk</span>
+      <span>Daynivo Kiosk</span>
     </footer>
   </div>
   <script src="kiosk.js"></script>