chore: restructure project into backend and frontend folders

- Move all frontend code to frontend/ directory
- Add backend/ with Go project structure (cmd, internal, pkg)
- Add docker-compose.yml for orchestration

frontend/src/main.tsx

@@ -0,0 +1,21 @@
+import { StrictMode } from 'react'
+import { createRoot } from 'react-dom/client'
+import './index.css'
+import App from './App.tsx'
+import { mockDeliveries } from './utils/mockData'
+import { useDeliveryStore } from './stores/deliveryStore'
+
+// Seed mock data if no data exists
+const stored = localStorage.getItem('delivery-tracker-data')
+if (!stored) {
+  const store = useDeliveryStore.getState()
+  mockDeliveries.forEach(delivery => {
+    store.addDelivery(delivery)
+  })
+}
+
+createRoot(document.getElementById('root')!).render(
+  <StrictMode>
+    <App />
+  </StrictMode>,
+)