Add listener spectrum visualizer

style.css

@@ -1380,7 +1380,8 @@ input[type=range] {
 }
 
 #viz-A,
-#viz-B {
+#viz-B,
+#viz-listener {
     height: 80px !important;
 }
 
@@ -2413,6 +2414,12 @@ input[type=range] {
     backdrop-filter: blur(10px);
 }
 
+#viz-listener {
+    width: 100%;
+    display: block;
+    margin: 20px 0;
+}
+
 .now-playing {
     text-align: center;
     font-family: 'Orbitron', sans-serif;
@@ -2559,6 +2566,11 @@ input[type=range] {
     .volume-control label {
         font-size: 0.9rem;
     }
+
+    #viz-listener {
+        height: 60px !important;
+        margin: 15px 0;
+    }
 }
 
 /* Hide landscape prompt globally when listening-active class is present */