i18n: Fix last hardcoded German error string in export function

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/static/js/app.js

@@ -2032,7 +2032,7 @@ const App = {
             const response = await API.exportIncident(this.currentIncidentId, format, scope);
             if (!response.ok) {
                 const err = await response.json().catch(() => ({}));
-                throw new Error(err.detail || 'Fehler ' + response.status);
+                throw new Error(err.detail || LangManager.t('err.generic') + ' ' + response.status);
             }
             const blob = await response.blob();
             const disposition = response.headers.get('Content-Disposition') || '';