Add browser call-in page and update host dashboard for browser callers

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

frontend/index.html

@@ -53,7 +53,7 @@
 
             <!-- Call Queue -->
             <section class="queue-section">
-                <h2>Incoming Calls</h2>
+                <h2>Incoming Calls <a href="/call-in" target="_blank" style="font-size:0.6em;font-weight:normal;color:var(--accent);">Call-in page</a></h2>
                 <div id="call-queue" class="call-queue">
                     <div class="queue-empty">No callers waiting</div>
                 </div>