Add read-only web dashboard MVP

Adds a disabled-by-default loopback web dashboard MVP with read-only control-plane views, prompt preview redaction, Vite React UI, and validation coverage.

apps/dashboard/src/main.tsx

@@ -0,0 +1,16 @@
+import { StrictMode } from 'react';
+import { createRoot } from 'react-dom/client';
+
+import App from './App';
+
+const root = document.getElementById('root');
+
+if (!root) {
+  throw new Error('Dashboard root element was not found');
+}
+
+createRoot(root).render(
+  <StrictMode>
+    <App />
+  </StrictMode>,
+);