Gracefully handle JWT expired and warn user to re-login

src/App.tsx

@@ -322,7 +322,7 @@ export default function App() {
     
     setIsSavingAll(true);
     let failedArticles: string[] = [];
-    const token = session?.access_token;
+    let jwtExpired = false;
     
     try {
       for (const [articleNo, { newData, originalData, articleName }] of entries) {
@@ -343,12 +343,17 @@ export default function App() {
         } else {
           setRowStatuses(prev => ({ ...prev, [articleNo]: 'error' }));
           failedArticles.push(`${articleNo} [${result.error || 'Unknown error'}]`);
+          if (result.error?.includes('401') || result.error?.includes('JWT expired')) {
+            jwtExpired = true;
+          }
         }
       }
 
       console.log('[handleSaveAll] Finished loop. Failed:', failedArticles.length);
       
-      if (failedArticles.length > 0) {
+      if (jwtExpired) {
+        alert("Tu sesión ha caducado (JWT expired). Por favor, haz clic en el botón de Cerrar Sesión (Sign out) arriba a la derecha y vuelve a iniciar sesión para guardar tus cambios.");
+      } else if (failedArticles.length > 0) {
         alert(`Failed to save items:\n\n${failedArticles.join('\n')}\n\nPlease try again.`);
       } else {
         setAppState(prev => ({ ...prev, hasUnsavedChanges: false }));