feat: add chatbox widget and dynamic nav links from dashboard API

- Add ChatboxWidget component (src/chatbox.jsx) with business hours check
- Update nav.jsx to fetch links dynamically from /api/public/links
- Wire ChatboxWidget into app.jsx
- Add chatbox.jsx script tag to index.html

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

index.html

@@ -204,6 +204,7 @@
     <script type="text/babel" src="src/agent-showcase.jsx"></script>
     <script type="text/babel" src="src/timeline-contact.jsx"></script>
     <script type="text/babel" src="src/command-palette.jsx"></script>
+    <script type="text/babel" src="src/chatbox.jsx"></script>
     <script type="text/babel" src="src/app.jsx"></script>
   </body>
 </html>