Add idents playback section — loads from idents/ folder, plays on ads channel

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

frontend/index.html

@@ -112,6 +112,16 @@
                 </div>
             </section>
 
+            <!-- Idents -->
+            <section class="music-section">
+                <h2>Idents</h2>
+                <select id="ident-select"></select>
+                <div class="music-controls">
+                    <button id="ident-play-btn">Play Ident</button>
+                    <button id="ident-stop-btn">Stop</button>
+                </div>
+            </section>
+
             <!-- Sound Effects -->
             <section class="sounds-section">
                 <h2>Sounds</h2>
@@ -240,6 +250,6 @@
         </div>
     </div>
 
-    <script src="/js/app.js?v=17"></script>
+    <script src="/js/app.js?v=18"></script>
 </body>
 </html>