Add lesson retrieval functionality in VocabController and VocabService

- Introduced a new method in VocabService to fetch lesson details, including access control based on user ownership and lesson visibility.
- Updated VocabController to wrap the new method for user access.
- Added a new route in VocabRouter to handle requests for specific lessons.
- Enhanced VocabCourseListView to support navigation to individual lesson views, improving user experience in accessing lesson content.

frontend/src/router/socialRoutes.js

@@ -99,6 +99,13 @@ const socialRoutes = [
         props: true,
         meta: { requiresAuth: true }
     },
+    {
+        path: '/socialnetwork/vocab/courses/:courseId/lessons/:lessonId',
+        name: 'VocabLesson',
+        component: () => import('../views/social/VocabLessonView.vue'),
+        props: true,
+        meta: { requiresAuth: true }
+    },
 ];
 
 export default socialRoutes;