Enhance browser phone with real-time updates and audible alerts

- Fix token expiration: Extend refresh buffer to 10 minutes for reliability
- Add real-time queue updates: Reduce polling to 5 seconds for instant feedback
- Implement audible alert system: 30-second repeating notifications with user toggle
- Optimize Discord/Slack notifications: Non-blocking requests for immediate delivery
- Add persistent alert preferences: Toggle button with localStorage integration
- Clean up debug file: Remove unused debug-phone-numbers.php

🤖 Generated with [Claude Code](https://claude.ai/code)

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

assets/css/browser-phone-frontend.css

@@ -434,10 +434,33 @@
 .queue-actions {
     display: flex;
     gap: 8px;
+    flex-wrap: wrap;
 }
 
 .queue-actions .twp-btn {
     flex: 1;
+    min-width: 80px;
+}
+
+/* Alert Toggle Button */
+#twp-alert-toggle {
+    position: relative;
+}
+
+#twp-alert-toggle.alert-on {
+    background-color: #28a745 !important;
+    border-color: #28a745;
+    color: white;
+}
+
+#twp-alert-toggle.alert-off {
+    background-color: #6c757d !important;
+    border-color: #6c757d;
+    color: white;
+}
+
+#twp-alert-toggle:hover {
+    opacity: 0.8;
 }
 
 .twp-btn-secondary {