feat: 添加数据库索引优化查询性能

refactor(前端): 使用useMemo和useCallback优化性能
perf(后端): 优化统计查询性能
style: 统一前端样式定义
build: 添加创建索引脚本

backend/models/Device.js

@@ -72,7 +72,15 @@ const Device = sequelize.define('Device', {
   }
 }, {
   tableName: 'devices',
-  timestamps: true
+  timestamps: true,
+  indexes: [
+    { fields: ['status'] },
+    { fields: ['type'] },
+    { fields: ['rackId'] },
+    { fields: ['createdAt'] },
+    { fields: ['status', 'type'] },
+    { fields: ['name'] }
+  ]
 });
 
 // 关联关系