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/users.go

@@ -11,6 +11,7 @@ import (
 	"verification-platform-backend/pkg/utils"
 
 	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
 )
 
 type UserWithStatus struct {
@@ -192,6 +193,28 @@ func handleGetUsers(c *gin.Context) {
 	offlineCount := 0
 	bannedCount := 0
 
+	userIDs := make([]uint, len(users))
+	for i, u := range users {
+		userIDs[i] = u.ID
+	}
+
+	deviceCountMap := make(map[uint]int)
+	if len(userIDs) > 0 {
+		type DeviceCountResult struct {
+			UserID uint
+			Count  int
+		}
+		var deviceCounts []DeviceCountResult
+		database.DB.Model(&model.UserDevice{}).
+			Select("user_id, COUNT(*) as count").
+			Where("user_id IN ?", userIDs).
+			Group("user_id").
+			Find(&deviceCounts)
+		for _, dc := range deviceCounts {
+			deviceCountMap[dc.UserID] = dc.Count
+		}
+	}
+
 	usersWithStatus := make([]UserWithStatus, 0, len(users))
 	for _, user := range users {
 		log.Printf("[DEBUG] User ID=%d, Username=%s, LastLoginAt=%v, LastHeartbeatAt=%v", user.ID, user.Username, user.LastLoginAt, user.LastHeartbeatAt)
@@ -214,15 +237,12 @@ func handleGetUsers(c *gin.Context) {
 			bannedCount++
 		}
 
-		var deviceCount int64
-		database.DB.Model(&model.UserDevice{}).Where("user_id = ?", user.ID).Count(&deviceCount)
-
 		log.Printf("[DEBUG] 用户 %s (ID=%d) 余额: %f", user.Username, user.ID, user.Balance)
 
 		usersWithStatus = append(usersWithStatus, UserWithStatus{
 			AppUser:      user,
 			OnlineStatus: onlineStatus,
-			DeviceCount:  int(deviceCount),
+			DeviceCount:  deviceCountMap[user.ID],
 		})
 	}
 
@@ -705,22 +725,35 @@ func handleUpdateExpiry(c *gin.Context) {
 		}
 	} else {
 		if req.Type == "recharge" {
-			appUser.Balance += req.Amount
+			if err := database.DB.Model(&model.AppUser{}).Where("id = ?", appUser.ID).
+				Update("balance", gorm.Expr("balance + ?", req.Amount)).Error; err != nil {
+				response.Error(c, 500, "充值失败")
+				return
+			}
 		} else if req.Type == "deduct" {
-			if appUser.Balance < req.Amount {
+			result := database.DB.Model(&model.AppUser{}).Where("id = ? AND balance >= ?", appUser.ID, req.Amount).
+				Update("balance", gorm.Expr("balance - ?", req.Amount))
+			if result.Error != nil {
+				response.Error(c, 500, "扣费失败")
+				return
+			}
+			if result.RowsAffected == 0 {
 				response.Error(c, 400, "余额不足")
 				return
 			}
-			appUser.Balance -= req.Amount
 		} else {
 			response.Error(c, 400, "操作类型错误")
 			return
 		}
 	}
 
-	if err := database.DB.Save(&appUser).Error; err != nil {
-		response.Error(c, 500, "更新失败")
-		return
+	if app.BillingType == "balance" {
+		database.DB.Where("id = ?", appUser.ID).First(&appUser)
+	} else {
+		if err := database.DB.Save(&appUser).Error; err != nil {
+			response.Error(c, 500, "更新失败")
+			return
+		}
 	}
 
 	response.Success(c, appUser)