Add on-air toggle for phone call routing

When off air, callers hear a message and get disconnected. When on
air, calls route normally. Toggle button added to frontend header
with pulsing red ON AIR indicator.

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

frontend/css/style.css

@@ -54,6 +54,27 @@ header button {
     cursor: pointer;
 }
 
+.on-air-btn {
+    font-weight: 700;
+    text-transform: uppercase;
+    letter-spacing: 0.05em;
+    transition: background 0.2s;
+}
+
+.on-air-btn.off {
+    background: #666 !important;
+}
+
+.on-air-btn.on {
+    background: #cc2222 !important;
+    animation: on-air-pulse 2s ease-in-out infinite;
+}
+
+@keyframes on-air-pulse {
+    0%, 100% { opacity: 1; }
+    50% { opacity: 0.7; }
+}
+
 .new-session-btn {
     background: var(--accent) !important;
 }

frontend/index.html

@@ -11,6 +11,7 @@
         <header>
             <h1>Luke at The Roost</h1>
             <div class="header-buttons">
+                <button id="on-air-btn" class="on-air-btn off">OFF AIR</button>
                 <button id="new-session-btn" class="new-session-btn">New Session</button>
                 <button id="settings-btn">Settings</button>
             </div>

frontend/js/app.js

@@ -57,6 +57,24 @@ function initEventListeners() {
     // New Session
     document.getElementById('new-session-btn')?.addEventListener('click', newSession);
 
+    // On-Air toggle
+    const onAirBtn = document.getElementById('on-air-btn');
+    if (onAirBtn) {
+        fetch('/api/on-air').then(r => r.json()).then(data => {
+            updateOnAirBtn(onAirBtn, data.on_air);
+        });
+        onAirBtn.addEventListener('click', async () => {
+            const isOn = onAirBtn.classList.contains('on');
+            const res = await safeFetch('/api/on-air', {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({ on_air: !isOn }),
+            });
+            updateOnAirBtn(onAirBtn, res.on_air);
+            log(res.on_air ? 'Show is ON AIR — accepting calls' : 'Show is OFF AIR — calls get off-air message');
+        });
+    }
+
     // Server controls
     document.getElementById('restart-server-btn')?.addEventListener('click', restartServer);
     document.getElementById('stop-server-btn')?.addEventListener('click', stopServer);
@@ -772,6 +790,12 @@ function log(text) {
     addMessage('System', text);
 }
 
+function updateOnAirBtn(btn, isOn) {
+    btn.classList.toggle('on', isOn);
+    btn.classList.toggle('off', !isOn);
+    btn.textContent = isOn ? 'ON AIR' : 'OFF AIR';
+}
+
 
 function showStatus(text) {
     const status = document.getElementById('status');