优化TabPage中关闭按钮的布局，使其靠右显示

AutoRobot/Windows/Robot/Web/src/DockLayout/TabPage.vue

@@ -112,6 +112,7 @@ const closeTab = (tabId) => {
   color: white;
   font-size: 12px;
   user-select: none;
+  position: relative;
 }
 
 .tab-item.active {
@@ -134,13 +135,14 @@ const closeTab = (tabId) => {
 }
 
 .button-icon {
-  margin-left: 8px;
+  margin-left: auto;
   background: transparent;
   border: none;
   cursor: pointer;
   display: flex;
   align-items: center;
   justify-content: center;
+  flex-shrink: 0;
 }
 
 /* 确保在活动标签页中的按钮样式正确 */