修复试卷标题在没有分享人时的布局问题

- 将标题默认底部边距从12px改为0
- 当有分享标签时动态添加12px底部边距
- 确保无分享标签时标题位置协调

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

web/src/pages/ExamManagement.module.less

@@ -98,7 +98,7 @@
   text-align: left;
 
   .examTitle {
-    margin: 0 0 12px 0;
+    margin: 0;
     font-size: 20px;
     font-weight: 700;
     line-height: 1.3;

web/src/pages/ExamManagement.tsx

@@ -295,7 +295,12 @@ const ExamManagement: React.FC = () => {
                         <FileTextOutlined />
                       </div>
                       <div className={styles.coverInfo}>
-                        <h3 className={styles.examTitle}>{exam.title}</h3>
+                        <h3
+                          className={styles.examTitle}
+                          style={{ marginBottom: exam.is_shared && exam.shared_by ? '12px' : '0' }}
+                        >
+                          {exam.title}
+                        </h3>
                         {exam.is_shared && exam.shared_by && (
                           <Tag
                             icon={<ShareAltOutlined />}