style: 调整 LiveStreamCard 组件按钮的 margin 样式

将“立即观看”按钮的 margin-left 从 mx-auto 改为 ml-auto，使其靠右对齐

@@ -33,7 +33,7 @@
             <div class="w-5 h-5 rounded-full bg-gray-500 border border-white"></div>
           </div> -->
           <!-- <span class="text-white text-xs ml-1">{{ stream.viewers }}人在看</span> -->
-          <button class="mx-auto bg-green-500 text-white text-xs px-2 py-1 rounded">
+          <button class="ml-auto bg-green-500 text-white text-xs px-2 py-1 rounded">
             立即观看
           </button>
         </div>