feat(设备字段): 添加系统字段保护机制

为设备字段添加isSystem属性标记系统字段，防止误删核心字段
后端添加字段删除前的系统字段检查
前端在管理界面标记并禁用系统字段的删除操作
更新导入模板生成逻辑以适配动态字段配置
优化设备导入功能，支持字段名称变更

frontend/src/pages/DeviceFieldManagement.jsx

@@ -1,6 +1,6 @@
 import React, { useState, useEffect, useMemo } from 'react';
-import { Table, Button, Modal, Form, Input, Select, message, Card, Space, InputNumber, Switch, Tag, Statistic } from 'antd';
-import { PlusOutlined, EditOutlined, DeleteOutlined, AppstoreOutlined, FontSizeOutlined, NumberOutlined, CheckCircleOutlined, CalendarOutlined, FileTextOutlined } from '@ant-design/icons';
+import { Table, Button, Modal, Form, Input, Select, message, Card, Space, InputNumber, Switch, Tag, Statistic, Tooltip } from 'antd';
+import { PlusOutlined, EditOutlined, DeleteOutlined, AppstoreOutlined, FontSizeOutlined, NumberOutlined, CheckCircleOutlined, CalendarOutlined, FileTextOutlined, LockOutlined } from '@ant-design/icons';
 import axios from 'axios';
 
 const { Option = Select.Option } = Select;
@@ -317,7 +317,16 @@ function DeviceFieldManagement() {
       dataIndex: 'fieldName',
       key: 'fieldName',
       width: 150,
-      render: (text) => <span style={tableCellStyle}>{text}</span>
+      render: (text, record) => (
+        <Space>
+          <span style={tableCellStyle}>{text}</span>
+          {record.isSystem && (
+            <Tooltip title="系统字段，不可删除">
+              <LockOutlined style={{ color: '#f59e0b', fontSize: '14px' }} />
+            </Tooltip>
+          )}
+        </Space>
+      )
     },
     {
       title: '显示名称',
@@ -385,9 +394,23 @@ function DeviceFieldManagement() {
           <Button type="text" icon={<EditOutlined />} onClick={() => showModal(record)} style={editButtonStyle}>
             编辑
           </Button>
-          <Button type="text" danger icon={<DeleteOutlined />} onClick={() => handleDelete(record.fieldId)} style={deleteButtonStyle}>
-            删除
-          </Button>
+          {record.isSystem ? (
+            <Tooltip title="系统字段不可删除">
+              <Button 
+                type="text" 
+                danger 
+                icon={<DeleteOutlined />} 
+                disabled
+                style={{ ...deleteButtonStyle, opacity: 0.3, cursor: 'not-allowed' }}
+              >
+                删除
+              </Button>
+            </Tooltip>
+          ) : (
+            <Button type="text" danger icon={<DeleteOutlined />} onClick={() => handleDelete(record.fieldId)} style={deleteButtonStyle}>
+              删除
+            </Button>
+          )}
         </Space>
       ),
     },

frontend/src/pages/DeviceManagement.jsx

@@ -1879,13 +1879,40 @@ function DeviceManagement() {
             
             <div style={{ marginBottom: '20px', padding: '16px', background: 'linear-gradient(180deg, #fafafa 0%, #ffffff 100%)', borderRadius: '12px', border: '1px solid #f0f0f0' }}>
               <p style={{ fontWeight: '600', marginBottom: '8px', color: '#333' }}>CSV文件格式要求：</p>
-              <ul style={{ paddingLeft: '20px', marginBottom: '10px', color: '#666', fontSize: '13px' }}>
-                <li>必填字段：设备ID、设备名称、设备类型、型号、序列号、所在机柜ID、位置(U)、高度(U)、功率(W)、状态、购买日期、保修到期</li>
-                <li>可选字段：IP地址、描述</li>
-                <li>设备类型：server(服务器)、switch(交换机)、router(路由器)、storage(存储设备)</li>
-                <li>状态值：running(运行中)、maintenance(维护中)、offline(离线)、fault(故障)</li>
-                <li>日期格式：YYYY-MM-DD (例如：2023-01-01)</li>
-              </ul>
+              <div style={{ maxHeight: '200px', overflowY: 'auto' }}>
+                {(() => {
+                  // 获取必填字段
+                  const requiredFields = deviceFields.filter(f => f.visible && f.required);
+                  // 获取可选字段
+                  const optionalFields = deviceFields.filter(f => f.visible && !f.required);
+                  
+                  return (
+                    <>
+                      {requiredFields.length > 0 && (
+                        <div style={{ marginBottom: '8px' }}>
+                          <span style={{ color: '#d93025', fontWeight: '500' }}>必填字段：</span>
+                          <span style={{ color: '#666', fontSize: '13px' }}>
+                            {requiredFields.map(f => f.displayName).join('、')}
+                          </span>
+                        </div>
+                      )}
+                      {optionalFields.length > 0 && (
+                        <div style={{ marginBottom: '8px' }}>
+                          <span style={{ color: '#666', fontWeight: '500' }}>可选字段：</span>
+                          <span style={{ color: '#666', fontSize: '13px' }}>
+                            {optionalFields.map(f => f.displayName).join('、')}
+                          </span>
+                        </div>
+                      )}
+                    </>
+                  );
+                })()}
+                <ul style={{ paddingLeft: '20px', marginBottom: '10px', color: '#666', fontSize: '13px', marginTop: '12px' }}>
+                  <li>设备类型：server(服务器)、switch(交换机)、router(路由器)、storage(存储设备)、other(其他)</li>
+                  <li>状态值：running(运行中)、maintenance(维护中)、offline(离线)、fault(故障)</li>
+                  <li>日期格式：YYYY-MM-DD (例如：2023-01-01)</li>
+                </ul>
+              </div>
             </div>
             
             <div style={{ marginBottom: '20px' }}>
@@ -1894,7 +1921,7 @@ function DeviceManagement() {
                   下载导入模板
                 </Button>
               </a>
-              <span style={{ color: '#999', fontSize: '12px', marginLeft: '10px' }}>包含示例数据的CSV模板文件</span>
+              <span style={{ color: '#999', fontSize: '12px', marginLeft: '10px' }}>包含示例数据的CSV模板文件（根据当前字段配置生成）</span>
             </div>
             
             <Upload