email box empty styling

frontend/src/hooks/useMailboxMaturity.js

@@ -0,0 +1,26 @@
+import { useEffect, useState } from "react";
+
+function storageKey(accountId) {
+  return `agmail_had_mail_${accountId}`;
+}
+
+export function useMailboxMaturity(account, emails, loading) {
+  const [hadMail, setHadMail] = useState(() => {
+    if (!account?.id) return false;
+    return localStorage.getItem(storageKey(account.id)) === "1";
+  });
+
+  useEffect(() => {
+    if (!account?.id) return;
+    if (!loading && emails.length > 0) {
+      localStorage.setItem(storageKey(account.id), "1");
+      setHadMail(true);
+    }
+  }, [account?.id, emails.length, loading]);
+
+  const isBrandNew = Boolean(
+    account?.id && !loading && emails.length === 0 && !hadMail,
+  );
+
+  return { isBrandNew, hadMail };
+}