Update VocabCourseView to simplify lesson number display and improve table styling

- Changed the lesson number header to a simple "#" for clarity.
- Adjusted column widths for the lesson number to enhance layout consistency.
- Centered text alignment for lesson number cells to improve visual presentation.

frontend/src/views/social/VocabCourseView.vue

@@ -23,7 +23,7 @@
         <table class="lessons-table">
           <thead>
             <tr>
-              <th class="col-number">{{ $t('socialnetwork.vocab.courses.lessonNumber') }}</th>
+              <th class="col-number">#</th>
               <th class="col-title">{{ $t('socialnetwork.vocab.courses.title') }}</th>
               <th class="col-status">Status</th>
               <th class="col-actions">Aktionen</th>
@@ -284,10 +284,15 @@ export default {
 
 .lessons-table th.col-number,
 .lessons-table td.lesson-number {
-  width: 80px;
-  min-width: 80px;
-  max-width: 80px;
+  width: 50px;
+  min-width: 50px;
+  max-width: 50px;
   overflow: visible;
+  text-align: center;
+}
+
+.lessons-table th.col-number {
+  text-align: center;
 }
 
 .lessons-table th.col-title,
@@ -332,6 +337,8 @@ export default {
   font-weight: 600;
   color: #666;
   font-size: 0.95em;
+  text-align: center;
+  display: block;
 }
 
 .lesson-title {