style(chat-room): 更新按钮样式类名

- 将批量撤回按钮的样式类从 "red" 更改为 "button"
- 统一按钮样式类名为 "button" 以保持一致性

Author: csfwff

src/main/resources/skins/classic/chat-room.ftl

@@ -100,7 +100,7 @@
                                             批量撤回
                                         </button>
                                     </#if>
-                                    <button class="red" onclick="switchTheme()">切换样式：简约</button>
+                                    <button class="button" onclick="switchTheme()">切换样式：简约</button>
                                     <button class="button" onclick="ChatRoom.toggleSmoothMode()">流畅模式: <span id="smoothMode">关闭</span></button>
                                     <button class="button" onclick="ChatRoom.showSiGuoYar()">思过崖</button>
                                     <button class="button" onclick="ChatRoom.flashScreen()">清屏</button>