fix(geplante-nachrichten): cache rooms response 60s and pass Nextcloud errors through to frontend

backend/src/services/scheduledMessages.service.ts

@@ -309,14 +309,19 @@ async function remove(id: string): Promise<boolean> {
 
 // ── Rooms ────────────────────────────────────────────────────────────────────
 
+let roomsCache: { result: RoomsResult; expiresAt: number } | null = null;
+
 async function getRooms(): Promise<RoomsResult> {
+  if (roomsCache && Date.now() < roomsCache.expiresAt) {
+    return roomsCache.result;
+  }
   const creds = await getBotCredentials();
   if (!creds) {
     return { configured: false };
   }
   try {
     const conversations = await nextcloudService.getAllConversations(creds.username, creds.appPassword);
-    return {
+    const result: RoomsResult = {
       configured: true,
       data: conversations.map(c => ({
         token: c.token,
@@ -324,10 +329,12 @@ async function getRooms(): Promise<RoomsResult> {
         type: c.type,
       })),
     };
+    roomsCache = { result, expiresAt: Date.now() + 60_000 };
+    return result;
   } catch (error) {
     const msg = error instanceof Error ? error.message : String(error);
     logger.error('scheduledMessages.getRooms failed', { error: msg });
-    return { configured: true, data: [], error: msg };
+    return { configured: true, data: [], error: 'Verbindung zu Nextcloud fehlgeschlagen' };
   }
 }