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/cards.go

@@ -443,7 +443,14 @@ func handleGetCards(c *gin.Context) {
 		query = query.Where("cards.created_at <= ?", endDate+" 23:59:59")
 	}
 
-	if err := query.Order("cards.created_at DESC").Find(&cards).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.Order("cards.created_at DESC").Offset(offset).Limit(pageSize).Find(&cards).Error; err != nil {
 		fmt.Printf("[DEBUG] Error fetching cards: %v\n", err)
 		response.Error(c, 500, "获取卡密列表失败")
 		return
@@ -451,7 +458,13 @@ func handleGetCards(c *gin.Context) {
 
 	fmt.Printf("[DEBUG] Found %d cards for user %d\n", len(cards), userID)
 
-	response.Success(c, cards)
+	response.Success(c, gin.H{
+		"cards":      cards,
+		"total":      total,
+		"page":       page,
+		"page_size":  pageSize,
+		"total_page": (total + int64(pageSize) - 1) / int64(pageSize),
+	})
 }
 
 func handleCreateCards(c *gin.Context) {
@@ -742,10 +755,8 @@ func handleBatchGenerateCards(c *gin.Context) {
 		}
 
 		totalCost := float64(req.Count) * cardType.Price
-		fmt.Printf("[DEBUG] Total cost: %f, Balance: %f\n", totalCost, agentUser.Balance)
 
 		if agentUser.Balance < totalCost {
-			fmt.Printf("[DEBUG] Insufficient balance\n")
 			response.Error(c, 400, "余额不足")
 			return
 		}
@@ -757,12 +768,18 @@ func handleBatchGenerateCards(c *gin.Context) {
 			}
 		}()
 
-		if err := tx.Model(&agentUser).Update("balance", agentUser.Balance-totalCost).Error; err != nil {
+		result := tx.Model(&model.User{}).Where("id = ? AND balance >= ?", agentUser.ID, totalCost).
+			Update("balance", gorm.Expr("balance - ?", totalCost))
+		if result.Error != nil {
 			tx.Rollback()
-			fmt.Printf("[DEBUG] Update balance error: %v\n", err)
 			response.Error(c, 500, "扣款失败")
 			return
 		}
+		if result.RowsAffected == 0 {
+			tx.Rollback()
+			response.Error(c, 400, "余额不足")
+			return
+		}
 
 		cards := make([]model.Card, 0, req.Count)
 		for i := 0; i < req.Count; i++ {