Enhance VocabService logging and update VocabCourseListView state management

- Added debug logging in VocabService to track course retrieval details, aiding in troubleshooting and performance monitoring.
- Updated VocabCourseListView to include additional state properties for managing share codes and search functionality, improving user experience and interaction capabilities.

backend/services/vocabService.js

@@ -615,6 +615,15 @@ export default class VocabService {
       order: [['createdAt', 'DESC']]
     });
 
+    // Debug-Logging (kann später entfernt werden)
+    console.log(`[getCourses] Gefunden: ${courses.length} Kurse`, {
+      userId: user.id,
+      languageId,
+      nativeLanguageId,
+      search,
+      where: JSON.stringify(where, null, 2)
+    });
+
     const coursesData = courses.map(c => c.get({ plain: true }));
     
     // Lade Sprachnamen für alle Kurse