feat: add frontend as flat files (was submodule)

frontend/src/App.jsx

@@ -0,0 +1,30 @@
+import { useState } from 'react'
+import { IS_DEV } from './env'
+import DevBanner from './components/DevBanner'
+import Hero from './components/Hero'
+import GelShowcase from './components/GelShowcase'
+import KerboulistanBanner from './components/KerboulistanBanner'
+import GameCanvas from './components/GameCanvas'
+import Footer from './components/Footer'
+
+function App() {
+  const [isPlaying, setIsPlaying] = useState(false)
+
+  if (isPlaying) {
+    return <GameCanvas onBack={() => setIsPlaying(false)} />
+  }
+
+  return (
+    <div className="min-h-screen">
+      <DevBanner />
+      {/* Offset content when dev banner is visible */}
+      {IS_DEV && <div className="h-8" />}
+      <Hero onPlay={() => setIsPlaying(true)} />
+      <GelShowcase />
+      <KerboulistanBanner />
+      <Footer />
+    </div>
+  )
+}
+
+export default App