code refactoring

frontend/src/components/LoadingBackdrop.tsx

@@ -0,0 +1,18 @@
+import { Backdrop, CircularProgress } from '@mui/material'
+import { useRecoilValue } from 'recoil'
+import { loadingAtom } from '../atoms/ui'
+
+const LoadingBackdrop: React.FC = () => {
+  const isLoading = useRecoilValue(loadingAtom)
+
+  return (
+    <Backdrop
+      sx={{ color: '#fff', zIndex: (theme) => theme.zIndex.drawer + 1 }}
+      open={!isLoading}
+    >
+      <CircularProgress color="primary" />
+    </Backdrop>
+  )
+}
+
+export default LoadingBackdrop