fix: use official ext-apps useApp hook to fix blank MCP App rendering

The custom useToolData hook had lifecycle issues that prevented the UI
from rendering in Claude Desktop/web: no appInfo in App constructor,
unhandled connect() Promise, app.close() on unmount conflicting with
React Strict Mode. Switched to the official useApp hook from
@modelcontextprotocol/ext-apps/react which handles initialization
handshake, handler registration, and cleanup correctly.

Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en

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

ui-apps/src/apps/operation-result/App.tsx

@@ -5,10 +5,18 @@ import { useToolData } from '@shared/hooks/useToolData';
 import type { OperationResultData } from '@shared/types';
 
 export default function App() {
-  const data = useToolData<OperationResultData>();
+  const { data, error, isConnected } = useToolData<OperationResultData>();
+
+  if (error) {
+    return <div style={{ padding: '16px', color: '#ef4444' }}>Error: {error}</div>;
+  }
+
+  if (!isConnected) {
+    return <div style={{ padding: '16px', color: '#9ca3af' }}>Connecting...</div>;
+  }
 
   if (!data) {
-    return <div style={{ padding: '16px', color: 'var(--n8n-text-muted)' }}>Loading...</div>;
+    return <div style={{ padding: '16px', color: '#9ca3af' }}>Waiting for data...</div>;
   }
 
   const isSuccess = data.status === 'success';