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>

src/app.jsx

@@ -82,6 +82,7 @@ function App() {
       <T.Footer />
 
       <T.CommandPalette open={paletteOpen} onClose={() => setPaletteOpen(false)} />
+      <T.ChatboxWidget />
 
       <window.TweaksPanel title="Tweaks">
         <window.TweakSection label="Theme" />