introduces useLocalStorage hook

frontend/src/hooks/useLocalStorage.ts

@@ -0,0 +1,18 @@
+import { useState, useEffect } from "react";
+
+export default function useLocalStorage(key: string, defaultValue: unknown) {
+  const [value, setValue] = useState(() => {
+    const storedValue = localStorage.getItem(key);
+    if (storedValue) {
+      return JSON.parse(storedValue);
+    }
+    return defaultValue;
+  });
+
+  useEffect(() => {
+    if (value === undefined) return;
+    localStorage.setItem(key, JSON.stringify(value));
+  }, [value, key]);
+
+  return [value, setValue];
+}