style(main): 侧边栏改浅色，与内容区/登录页视觉统一

- Sider 传 theme=light（side-menu 默认值同步改 light），白底 + 右侧细分隔线
- 折叠态图标/tooltip 文字色随 light 主题自动变深灰
- tag-nav 顶条 #F0F0F0 → #f5f7fa 微调至同色系

src/components/main/components/side-menu/side-menu.vue

@@ -48,7 +48,7 @@ export default {
     },
     theme: {
       type: String,
-      default: 'dark'
+      default: 'light'
     },
     rootIconSize: {
       type: Number,

src/components/main/main.less

@@ -26,7 +26,7 @@
   .tag-nav-wrapper{
     padding: 0;
     height:40px;
-    background:#F0F0F0;
+    background:#f5f7fa;
   }
   .content-wrapper{
     padding: 18px;
@@ -36,6 +36,9 @@
     background: #fff;
   }
   .left-sider{
+    // 浅色侧边栏：与内容区统一，仅以右边框区分
+    background: #fff;
+    box-shadow: 1px 0 0 #e8ecf4;
     .ivu-layout-sider-children{
       overflow-y: scroll;
       margin-right: -18px;

src/components/main/main.vue

@@ -1,7 +1,7 @@
 <template>
   <Layout style="height: 100%" class="main">
-    <Sider hide-trigger collapsible :width="256" :collapsed-width="64" v-model="collapsed" class="left-sider" :style="{overflow: 'hidden'}">
-      <side-menu accordion ref="sideMenu" :active-name="$route.name" :collapsed="collapsed" @on-select="turnToPage" :menu-list="menuList">
+    <Sider hide-trigger collapsible :width="256" :collapsed-width="64" v-model="collapsed" class="left-sider sider-light" :style="{overflow: 'hidden'}">
+      <side-menu accordion ref="sideMenu" :active-name="$route.name" :collapsed="collapsed" theme="light" @on-select="turnToPage" :menu-list="menuList">
         <!-- 需要放在菜单上面的内容，如Logo，写在side-menu标签内部，如下 -->
         <div class="logo-con" style="text-align: center">
           <img v-show="!collapsed" :src="maxLogo" key="max-logo" />