fix: persist tender preparation and correct calendar export

src/App.jsx

@@ -39,12 +39,14 @@ import { LoginPage } from './components/LoginPage';
 import { LandingPage } from './components/LandingPage';
 
 const MainContent = () => {
-  const { activeTab, isAdmin } = useApp();
+  const { activeTab, isAdmin, saveError, savingCount } = useApp();
 
   return (
     <main className="max-w-[1600px] mx-auto px-4 pb-12">
       {/* 3-Column Main View */}
       <KotaUyarisi />
+      {savingCount > 0 && <p role="status" className="p-3 bg-blue-50 text-blue-900">Kaydediliyor…</p>}
+      {saveError && <p role="alert" className="p-3 bg-red-50 text-red-900 border border-red-200 rounded-lg">{saveError} Değişiklik kaydedilmedi; tekrar deneyin.</p>}
 
       {activeTab === 'list' && (
         <>