feat: add frontend source (fix submodule), compact node design

- Remove nested .git from Vite scaffold
- Horizontal node layout: icon left, label+IP right, reduced height

frontend/src/main.tsx

@@ -0,0 +1,10 @@
+import { StrictMode } from 'react'
+import { createRoot } from 'react-dom/client'
+import './index.css'
+import App from './App.tsx'
+
+createRoot(document.getElementById('root')!).render(
+  <StrictMode>
+    <App />
+  </StrictMode>,
+)