Enhance VocabService and VocabCourseView for improved multiple choice handling and table layout

- Updated VocabService to support multiple correct answers in multiple choice exercises, allowing for better answer validation and user feedback.
- Enhanced the extraction of correct answers and alternatives to accommodate both single and multiple correct indices.
- Improved CSS styles in VocabCourseView for better table layout, including adjustments for overflow handling and vertical alignment, enhancing overall user experience.

frontend/src/views/social/VocabCourseView.vue

@@ -257,6 +257,11 @@ export default {
   table-layout: fixed;
 }
 
+.lessons-table th,
+.lessons-table td {
+  box-sizing: border-box;
+}
+
 .lessons-table thead {
   background: #f8f9fa;
 }
@@ -276,12 +281,14 @@ export default {
   width: 80px;
   min-width: 80px;
   max-width: 80px;
+  overflow: visible;
 }
 
 .lessons-table th.col-title,
 .lessons-table td.lesson-title {
   width: auto;
   min-width: 200px;
+  overflow: visible;
 }
 
 .lessons-table th.col-status,
@@ -289,6 +296,8 @@ export default {
   width: 200px;
   min-width: 200px;
   max-width: 200px;
+  overflow: visible;
+  word-wrap: break-word;
 }
 
 .lessons-table th.col-actions,
@@ -296,6 +305,7 @@ export default {
   width: 250px;
   min-width: 250px;
   max-width: 250px;
+  overflow: visible;
 }
 
 .lessons-table tbody tr {
@@ -308,13 +318,15 @@ export default {
 
 .lessons-table td {
   padding: 15px;
-  vertical-align: middle;
+  vertical-align: top;
 }
 
 .lesson-number {
   font-weight: 600;
   color: #666;
   font-size: 0.95em;
+  vertical-align: top;
+  padding-top: 15px;
 }
 
 .lesson-title {
@@ -340,11 +352,9 @@ export default {
   flex-direction: column;
   gap: 5px;
   align-items: flex-start;
-  justify-content: center;
-  min-height: 60px;
+  justify-content: flex-start;
   white-space: nowrap;
-  overflow: hidden;
-  text-overflow: ellipsis;
+  overflow: visible;
 }
 
 .badge.completed {
@@ -372,7 +382,7 @@ export default {
   display: flex;
   gap: 8px;
   flex-wrap: wrap;
-  align-items: center;
+  align-items: flex-start;
   justify-content: flex-start;
 }