feat: 优化前端界面布局和响应式设计

- 为表格添加空数据提示组件
- 根据设备类型动态调整抽屉组件大小
- 优化表格列宽和显示效果
- 调整描述组件的列数布局
- 在重置用户状态时清除用户信息

frontend/src/views/monitor/online/index.vue

@@ -67,7 +67,7 @@
         <el-table-column v-if="tableColumns.find(col => col.prop === 'selection')?.show" type="selection" min-width="55" align="center" />
         <el-table-column v-if="tableColumns.find(col => col.prop === 'index')?.show" type="index" fixed label="序号" min-width="60" />
         <el-table-column v-if="tableColumns.find(col => col.prop === 'session_id')?.show" key="session_id" label="会话编号" prop="session_id" min-width="250" show-overflow-tooltip/>
-        <el-table-column v-if="tableColumns.find(col => col.prop === 'ipaddr')?.show" key="ipaddr" label="IP地址" prop="ipaddr" min-width="120">
+        <el-table-column v-if="tableColumns.find(col => col.prop === 'ipaddr')?.show" key="ipaddr" label="IP地址" prop="ipaddr" min-width="150" show-overflow-tooltip>
           <template #default="scope">
             <el-text>{{ scope.row.ipaddr }}</el-text>
             <CopyButton v-if="scope.row.ipaddr" :text="scope.row.ipaddr" style="margin-left: 2px" />
@@ -75,8 +75,8 @@
         </el-table-column>
         <el-table-column v-if="tableColumns.find(col => col.prop === 'name')?.show" key="name" label="用户名" prop="name" min-width="80" />
         <el-table-column v-if="tableColumns.find(col => col.prop === 'user_name')?.show" key="user_name" label="用户姓名" prop="user_name" min-width="80" />
-        <el-table-column v-if="tableColumns.find(col => col.prop === 'login_location')?.show" key="login_location" label="登录位置" prop="login_location" min-width="80" />
-        <el-table-column v-if="tableColumns.find(col => col.prop === 'os')?.show" key="os" label="操作系统" prop="os" min-width="80" />
+        <el-table-column v-if="tableColumns.find(col => col.prop === 'login_location')?.show" key="login_location" label="登录位置" prop="login_location" min-width="280" show-overflow-tooltip/>
+        <el-table-column v-if="tableColumns.find(col => col.prop === 'os')?.show" key="os" label="操作系统" prop="os" min-width="120" />
         <el-table-column v-if="tableColumns.find(col => col.prop === 'login_time')?.show" key="login_time" label="登录时间" prop="login_time" min-width="180" />
         <el-table-column v-if="tableColumns.find(col => col.prop === 'operation')?.show" key="operation" fixed="right" label="操作" min-width="100">
           <template #default="scope">

frontend/src/views/monitor/server/index.vue

@@ -169,11 +169,10 @@
               </el-tooltip>
             </div>
           </template>
-          <el-table 
-            :data="server.disks" 
-            border 
-            
-          >
+          <el-table :data="server.disks" border >
+            <template #empty>
+              <el-empty :image-size="80" description="暂无数据" />
+            </template>
             <el-table-column 
               label="盘符路径" 
               prop="dir_name"