style(24-01): add recording button pulse animation

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

jam-ui/src/assets/scss/custom/_session.scss

@@ -82,3 +82,21 @@ table.vu td {
     width:12px;
     height:12px;
 }
+
+// Recording button active state
+.btn-recording-active {
+    animation: recording-pulse 1.5s ease-in-out infinite;
+
+    &:hover {
+        animation: none;
+    }
+}
+
+@keyframes recording-pulse {
+    0%, 100% {
+        opacity: 1;
+    }
+    50% {
+        opacity: 0.7;
+    }
+}