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.

frontend/src/views/social/VocabCourseView.vue

@@ -8,6 +8,9 @@
       <div class="course-info">
         <span>{{ $t('socialnetwork.vocab.courses.difficulty') }}: {{ course.difficultyLevel }}</span>
         <span v-if="course.isPublic">{{ $t('socialnetwork.vocab.courses.public') }}</span>
+        <span v-if="course.shareCode && isOwner" class="share-code">
+          {{ $t('socialnetwork.vocab.courses.shareCode') }}: <code>{{ course.shareCode }}</code>
+        </span>
       </div>
 
       <div v-if="isOwner" class="owner-actions">
@@ -206,6 +209,18 @@ export default {
   gap: 15px;
   margin: 15px 0;
   color: #666;
+  flex-wrap: wrap;
+}
+
+.share-code {
+  font-family: monospace;
+}
+
+.share-code code {
+  background: #f0f0f0;
+  padding: 2px 6px;
+  border-radius: 3px;
+  font-size: 0.9em;
 }
 
 .owner-actions {