feat(VocabService, AppHeader): enhance timeout configuration and update ad display settings

- Updated the VocabService to allow configurable timeout for responses, defaulting to 300 seconds if not set or invalid.
- Modified AppHeader component to change ad format to horizontal and adjusted responsive settings for better display consistency.
- Ensured proper height settings for ad elements to maintain layout integrity across different screen sizes.

backend/services/vocabService.js

@@ -2844,7 +2844,11 @@ export default class VocabService {
     }
 
     const controller = new AbortController();
-    const timeout = setTimeout(() => controller.abort(), 120000);
+    const configuredTimeout = Number(process.env.LLM_ASSISTANT_TIMEOUT_MS);
+    const timeoutMs = Number.isFinite(configuredTimeout) && configuredTimeout >= 30000
+      ? configuredTimeout
+      : 300000;
+    const timeout = setTimeout(() => controller.abort(), timeoutMs);
 
     const temperatureByMode = {
       explain: 0.4,
@@ -2878,7 +2882,7 @@ export default class VocabService {
     } catch (error) {
       const err = new Error(
         error?.name === 'AbortError'
-          ? 'Der Sprachassistent hat länger als zwei Minuten für eine Antwort gebraucht.'
+          ? 'Der Sprachassistent hat das Antwort-Zeitlimit überschritten.'
           : 'Der Sprachassistent konnte nicht erreicht werden.'
       );
       err.status = 502;