fix: 修复数据库配置和事务一致性问题

数据库配置:
- SQLite 开启 WAL 模式，读写可并发
- 设置 busy_timeout=5000ms 避免锁超时
- 设置 synchronous=NORMAL 平衡性能和安全
- SQLite MaxOpenConns 设为 1 避免并发写入冲突

事务修复:
- auth.go: 注册流程(用户+设备+会话)加入事务
- auth.go: 密码重置(修改密码+标记验证码)加入事务
- cards.go: 卡密使用加入事务，补充 UsedAt 字段
- cards.go: 代理商批量生成(扣款+生成卡密)加入事务
- extension.go: 充值(修改余额+记录)加入事务
- extension.go: 扣费(修改余额+记录)加入事务
- storage_config.go: 设置默认存储加入事务

backend/internal/router/admin/cards.go

@@ -618,19 +618,36 @@ func handleUseCard(c *gin.Context) {
 		return
 	}
 
+	tx := database.DB.Begin()
+	defer func() {
+		if r := recover(); r != nil {
+			tx.Rollback()
+		}
+	}()
+
 	var card model.Card
-	if err := database.DB.Where("card_key = ?", req.CardKey).First(&card).Error; err != nil {
+	if err := tx.Where("card_key = ?", req.CardKey).First(&card).Error; err != nil {
+		tx.Rollback()
 		response.Error(c, 404, "卡密不存在")
 		return
 	}
 
 	if card.Status != "unused" {
+		tx.Rollback()
 		response.Error(c, 400, "卡密已被使用或已禁用")
 		return
 	}
 
 	card.Status = "used"
-	database.DB.Save(&card)
+	now := time.Now()
+	card.UsedAt = &now
+	if err := tx.Save(&card).Error; err != nil {
+		tx.Rollback()
+		response.Error(c, 500, "卡密使用失败")
+		return
+	}
+
+	tx.Commit()
 
 	response.Success(c, gin.H{
 		"message": "卡密使用成功",
@@ -733,13 +750,50 @@ func handleBatchGenerateCards(c *gin.Context) {
 			return
 		}
 
-		if err := database.DB.Model(&agentUser).Update("balance", agentUser.Balance-totalCost).Error; err != nil {
+		tx := database.DB.Begin()
+		defer func() {
+			if r := recover(); r != nil {
+				tx.Rollback()
+			}
+		}()
+
+		if err := tx.Model(&agentUser).Update("balance", agentUser.Balance-totalCost).Error; err != nil {
+			tx.Rollback()
 			fmt.Printf("[DEBUG] Update balance error: %v\n", err)
 			response.Error(c, 500, "扣款失败")
 			return
 		}
 
-		fmt.Printf("[DEBUG] Balance updated successfully\n")
+		cards := make([]model.Card, 0, req.Count)
+		for i := 0; i < req.Count; i++ {
+			cardKey := req.Prefix + utils.GenerateRandomString(req.Length)
+			card := model.Card{
+				ApplicationID: req.ApplicationID,
+				CardTypeID:    req.CardTypeID,
+				CardKey:       cardKey,
+				CreatorID:     effectiveUserID,
+				Status:        "unused",
+			}
+			cards = append(cards, card)
+		}
+
+		fmt.Printf("[DEBUG] Generated %d cards, saving to database...\n", len(cards))
+
+		if err := tx.Create(&cards).Error; err != nil {
+			tx.Rollback()
+			fmt.Printf("[DEBUG] Database create error: %v\n", err)
+			response.Error(c, 500, "生成卡密失败")
+			return
+		}
+
+		tx.Commit()
+		fmt.Printf("[DEBUG] Successfully created %d cards\n", len(cards))
+
+		response.Success(c, gin.H{
+			"message": "批量生成成功",
+			"count":   req.Count,
+		})
+		return
 	}
 
 	cards := make([]model.Card, 0, req.Count)