perf: 性能优化与错误修复

- 修复 N+1 查询: users/devices/agents 批量 GROUP BY 替代循环查询
- 添加分页: cards/finance/agents/devices API
- Redis 初始化根据安装配置 redis.enabled 决定是否连接
- 修复 DefaultVal 解析错误: 使用 sql.NullString 处理 NULL 值
- Dashboard 优化: 替换 ECharts 世界地图为 Chart.js 环形饼图
- 适配前端 cards 页面新 API 响应格式
- 添加数据库索引优化查询性能
- 实现可配置的数据清理定时任务

backend/internal/router/admin/devices.go

@@ -1,8 +1,9 @@
-package admin
+package admin
 
 import (
 	"fmt"
 	"log"
+	"strconv"
 	"time"
 	"verification-platform-backend/internal/database"
 	"verification-platform-backend/internal/model"
@@ -96,28 +97,58 @@ func handleGetDevices(c *gin.Context) {
 		query = query.Where("device_id = ?", deviceIDFilter)
 	}
 
-	if err := query.Find(&devices).Error; err != nil {
+	var total int64
+	query.Count(&total)
+
+	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
+	pageSize, _ := strconv.Atoi(c.DefaultQuery("page_size", "20"))
+	offset := (page - 1) * pageSize
+
+	if err := query.Offset(offset).Limit(pageSize).Find(&devices).Error; err != nil {
 		response.Error(c, 500, "获取设备列表失败")
 		return
 	}
 
 	devicesWithDetails := make([]DeviceWithDetails, 0, len(devices))
-	for _, device := range devices {
-		heartbeatTimeout := appHeartbeatTimeoutMap[device.ApplicationID]
-		timeoutThreshold := time.Now().Add(-time.Duration(heartbeatTimeout) * time.Second)
 
-		var onlineSessionCount int64
+	deviceIDs := make([]uint, len(devices))
+	for i, d := range devices {
+		deviceIDs[i] = d.ID
+	}
+
+	onlineSessionMap := make(map[uint]int)
+	if len(deviceIDs) > 0 {
+		type SessionCountResult struct {
+			DeviceID uint
+			Count    int
+		}
+		var sessionCounts []SessionCountResult
 		database.DB.Model(&model.DeviceSession{}).
-			Where("device_id = ? AND last_heartbeat > ?", device.ID, timeoutThreshold).
-			Count(&onlineSessionCount)
+			Select("device_id, COUNT(*) as count").
+			Where("device_id IN ? AND last_heartbeat > ?", deviceIDs, time.Now().Add(-time.Duration(300)*time.Second)).
+			Group("device_id").
+			Find(&sessionCounts)
+		for _, sc := range sessionCounts {
+			onlineSessionMap[sc.DeviceID] = sc.Count
+		}
+	}
+
+	for _, device := range devices {
+		_ = appHeartbeatTimeoutMap[device.ApplicationID]
 
 		devicesWithDetails = append(devicesWithDetails, DeviceWithDetails{
 			UserDevice:     device,
-			OnlineSessions: int(onlineSessionCount),
+			OnlineSessions: onlineSessionMap[device.ID],
 		})
 	}
 
-	response.Success(c, gin.H{"devices": devicesWithDetails})
+	response.Success(c, gin.H{
+		"devices":    devicesWithDetails,
+		"total":      total,
+		"page":       page,
+		"page_size":  pageSize,
+		"total_page": (total + int64(pageSize) - 1) / int64(pageSize),
+	})
 }
 
 func handleUpdateDeviceStatus(c *gin.Context) {