修复中间预览区与右侧画布排版一致性

- 隐藏中间预览区滚动条,消除15px宽度差异
- 统一padding为20px,内容宽度均为500px
- .page-content行高改用CSS变量--pi-line-height
- #paginated-preview加入CSS变量选择器
- 去掉中间预览区右侧边框

view/admin/post/phone_image.html

@@ -83,27 +83,31 @@
 
         .render-preview-area {
             width: 540px;
-            overflow-y: auto;
-            border-right: 1px solid #e8e8e8;
+            overflow: hidden;
             background: #fff;
             flex-shrink: 0;
         }
 
         .render-preview-area .preview-header {
-            padding: 8px 15px;
+            padding: 8px 20px;
             background: #fafafa;
             border-bottom: 1px solid #e8e8e8;
             font-size: 13px;
             color: #999;
-            position: sticky;
-            top: 0;
-            z-index: 5;
         }
 
         #render-preview {
             min-height: 300px;
-            padding: 10px;
+            padding: 20px;
             box-sizing: border-box;
+            overflow-y: scroll;
+            overflow-x: hidden;
+            scrollbar-width: none;
+            -ms-overflow-style: none;
+        }
+
+        #render-preview::-webkit-scrollbar {
+            display: none;
         }
 
         .paginated-preview-area {