Add course retrieval by share code feature and enhance course search functionality

- Implemented a new endpoint in VocabController to retrieve courses using a share code.
- Updated VocabService to include logic for validating share codes and checking course access permissions.
- Enhanced course listing functionality with search and language filtering options in the frontend.
- Added a dialog for users to input share codes and search for courses, improving user experience.
- Updated internationalization files to include new strings for share code functionality and search features.

backend/services/vocabService.js

@@ -559,27 +559,101 @@ export default class VocabService {
     return course.get({ plain: true });
   }
 
-  async getCourses(hashedUserId, { includePublic = true, includeOwn = true } = {}) {
+  async getCourses(hashedUserId, { includePublic = true, includeOwn = true, languageId, search } = {}) {
     const user = await this._getUserByHashedId(hashedUserId);
 
     const where = {};
+    const andConditions = [];
+    
+    // Zugriffsbedingungen
     if (includeOwn && includePublic) {
-      where[Op.or] = [
-        { ownerUserId: user.id },
-        { isPublic: true }
-      ];
+      andConditions.push({
+        [Op.or]: [
+          { ownerUserId: user.id },
+          { isPublic: true }
+        ]
+      });
     } else if (includeOwn) {
       where.ownerUserId = user.id;
     } else if (includePublic) {
       where.isPublic = true;
     }
 
+    // Filter nach Sprache
+    if (languageId) {
+      where.languageId = Number(languageId);
+    }
+
+    // Suche nach Titel oder Beschreibung
+    if (search && search.trim()) {
+      const searchTerm = `%${search.trim()}%`;
+      andConditions.push({
+        [Op.or]: [
+          { title: { [Op.iLike]: searchTerm } },
+          { description: { [Op.iLike]: searchTerm } }
+        ]
+      });
+    }
+
+    // Kombiniere alle AND-Bedingungen
+    if (andConditions.length > 0) {
+      where[Op.and] = andConditions;
+    }
+
     const courses = await VocabCourse.findAll({
       where,
       order: [['createdAt', 'DESC']]
     });
 
-    return courses.map(c => c.get({ plain: true }));
+    const coursesData = courses.map(c => c.get({ plain: true }));
+    
+    // Lade Sprachnamen für alle Kurse
+    const languageIds = [...new Set(coursesData.map(c => c.languageId))];
+    if (languageIds.length > 0) {
+      const [languages] = await sequelize.query(
+        `SELECT id, name FROM community.vocab_language WHERE id IN (:languageIds)`,
+        {
+          replacements: { languageIds },
+          type: sequelize.QueryTypes.SELECT
+        }
+      );
+      const languageMap = new Map(languages.map(l => [l.id, l.name]));
+      coursesData.forEach(c => {
+        c.languageName = languageMap.get(c.languageId) || null;
+      });
+    }
+
+    return coursesData;
+  }
+
+  async getCourseByShareCode(hashedUserId, shareCode) {
+    const user = await this._getUserByHashedId(hashedUserId);
+    const code = typeof shareCode === 'string' ? shareCode.trim() : '';
+    
+    if (!code || code.length < 6 || code.length > 128) {
+      const err = new Error('Invalid share code');
+      err.status = 400;
+      throw err;
+    }
+
+    const course = await VocabCourse.findOne({
+      where: { shareCode: code }
+    });
+
+    if (!course) {
+      const err = new Error('Course not found');
+      err.status = 404;
+      throw err;
+    }
+
+    // Prüfe Zugriff (öffentlich oder Besitzer)
+    if (course.ownerUserId !== user.id && !course.isPublic) {
+      const err = new Error('Course is not public');
+      err.status = 403;
+      throw err;
+    }
+
+    return course.get({ plain: true });
   }
 
   async getCourse(hashedUserId, courseId) {