foundations: design tokens (light + dark) and CSS reset

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

src/main.tsx

@@ -1,9 +1,13 @@
 import { StrictMode } from 'react'
 import { createRoot } from 'react-dom/client'
+import { BrowserRouter } from 'react-router-dom'
 import App from './App'
+import './index.css'
 
 createRoot(document.getElementById('root')!).render(
   <StrictMode>
-    <App />
+    <BrowserRouter>
+      <App />
+    </BrowserRouter>
   </StrictMode>,
 )