Add WebSocket error handling with stack traces

Wrapped ws.onmessage in try-catch to capture full stack trace
when errors occur during message handling. This will help identify
where the 'Cannot read properties of undefined' error is coming from.

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

public/index.html

@@ -2458,6 +2458,7 @@
             ws = new WebSocket(`${protocol}//${window.location.host}`);
 
             ws.onmessage = (event) => {
+                try {
                     const data = JSON.parse(event.data);
                     console.log('WebSocket message:', data);
 
@@ -2525,6 +2526,10 @@
                     if (!['command_result', 'workflow_result', 'worker_update', 'execution_started', 'execution_status', 'workflow_created', 'workflow_deleted'].includes(data.type)) {
                         refreshData();
                     }
+                } catch (error) {
+                    console.error('Error handling WebSocket message:', error);
+                    console.error('Stack trace:', error.stack);
+                }
             };
 
             ws.onclose = () => {