feat: add frontend entry point, theme, and router

frontend/src/main.tsx

@@ -0,0 +1,15 @@
+import React from 'react'
+import ReactDOM from 'react-dom/client'
+import { ThemeProvider } from '@mui/material/styles'
+import CssBaseline from '@mui/material/CssBaseline'
+import App from './App'
+import { theme } from './theme'
+
+ReactDOM.createRoot(document.getElementById('root')!).render(
+  <React.StrictMode>
+    <ThemeProvider theme={theme}>
+      <CssBaseline />
+      <App />
+    </ThemeProvider>
+  </React.StrictMode>
+)