Refactor app state to be a state machine with access selectors

web/pages/index.tsx

@@ -1,10 +1,5 @@
-import { RecoilRoot } from 'recoil';
 import Main from '../components/layouts/Main';
 
 export default function Home() {
-  return (
-    <RecoilRoot>
-      <Main />
-    </RecoilRoot>
-  );
+  return <Main />;
 }