Add endpoint to retrieve all available languages in VocabController and VocabRouter

- Introduced a new method in VocabService to list all languages from the database.
- Updated VocabController to wrap the new method for user access.
- Added a new route in VocabRouter to handle requests for all languages.
- Modified VocabCourseListView to utilize the new endpoint for loading languages, enhancing the course selection experience.

backend/services/vocabService.js

@@ -147,6 +147,24 @@ export default class VocabService {
     return { languages: rows };
   }
 
+  async listAllLanguages() {
+    // Gibt alle verfügbaren Sprachen zurück (für Kursliste)
+    const rows = await sequelize.query(
+      `
+      SELECT
+        id,
+        name
+      FROM community.vocab_language
+      ORDER BY name ASC
+      `,
+      {
+        type: sequelize.QueryTypes.SELECT,
+      }
+    );
+
+    return { languages: rows };
+  }
+
   async listLanguagesForMenu(userId) {
     // userId ist die numerische community.user.id
     const rows = await sequelize.query(