.NET: Add DevUI package for .NET (#1603)

* Implement DevUI

* Review feedback

* Fix build

python/packages/devui/frontend/src/main.tsx

@@ -3,6 +3,10 @@ import { createRoot } from 'react-dom/client'
 import './index.css'
 import App from './App.tsx'
 import { ThemeProvider } from "./components/theme-provider"
+import { initStreamingState } from "./services/api"
+
+// Initialize streaming state management (clears expired states)
+initStreamingState();
 
 createRoot(document.getElementById('root')!).render(
   <StrictMode>