style(PdfViewer): 调整缩放按钮样式和布局

将放大和缩小按钮的图标样式调整为统一大小和颜色
移除注释掉的旧代码，保持代码整洁

 <!--
  * @Date: 2025-01-21
  * @LastEditors: hookehuyr hookehuyr@gmail.com
- * @LastEditTime: 2025-10-22 15:25:21
+ * @LastEditTime: 2025-10-22 15:53:46
  * @FilePath: /mlaj/src/components/ui/PdfViewer.vue
  * @Description: PDF预览组件 - 使用pdf-vue3库
 -->
@@ -65,7 +65,10 @@
             >
                 <van-button class="zoom-btn zoom-close-btn" type="default" icon="cross" round @click="handleClose" />
                 <!-- <van-button class="zoom-btn zoom-in-btn" type="default" icon="plus" round @click="zoomIn" /> -->
-                <font-awesome-icon icon="magnifying-glass-plus" class="text-2xl text-gray-600 ml-2 mr-2" @click="zoomIn" />
+                <div class="zoom-btn flex items-center justify-center" @click="zoomIn">
+                    <font-awesome-icon icon="magnifying-glass-plus" class="text-xl ml-2 mr-2" style="color: #000;" />
+                </div>
+                <!-- <font-awesome-icon icon="magnifying-glass-plus" class="text-2xl text-gray-600 ml-2 mr-2" @click="zoomIn" /> -->
                 <div class="page-jump" @click="focusPageInput">
                     <span class="page-display">{{ currentPage }} / {{ totalPages || 0 }}</span>
                     <input
@@ -81,7 +84,9 @@
                     />
                 </div>
                 <!-- <van-button class="zoom-btn zoom-out-btn" type="default" icon="minus" round @click="zoomOut" /> -->
-                <font-awesome-icon icon="magnifying-glass-minus" class="text-2xl text-gray-600 ml-2 mr-2" @click="zoomOut" />
+                <div class="zoom-btn flex items-center justify-center" @click="zoomOut">
+                    <font-awesome-icon icon="magnifying-glass-minus" class="text-xl ml-2 mr-2" style="color: #000;" />
+                </div>
                 <van-button class="zoom-btn zoom-reset-btn" type="default" round @click="resetZoom">
                     <van-icon name="replay" size="16" />
                 </van-button>