feat: Add user notification settings with quota warning and multiple notification methods

- Implement user notification settings with email and webhook options
- Add new user settings for quota warning threshold and notification preferences
- Create backend API and database support for user notification configuration
- Enhance frontend personal settings with notification configuration UI
- Support custom notification email and webhook URL
- Add service layer for sending user notifications

constant/env.go

@@ -44,5 +44,5 @@ func InitEnv() {
 	}
 }
 
-// 是否生成初始令牌，默认关闭。
+// GenerateDefaultToken 是否生成初始令牌，默认关闭。
 var GenerateDefaultToken = common.GetEnvOrDefaultBool("GENERATE_DEFAULT_TOKEN", false)

constant/user_setting.go

@@ -0,0 +1,14 @@
+package constant
+
+var (
+	UserSettingNotifyType            = "notify_type"             // QuotaWarningType 额度预警类型
+	UserSettingQuotaWarningThreshold = "quota_warning_threshold" // QuotaWarningThreshold 额度预警阈值
+	UserSettingWebhookUrl            = "webhook_url"             // WebhookUrl webhook地址
+	UserSettingWebhookSecret         = "webhook_secret"          // WebhookSecret webhook密钥
+	UserSettingNotificationEmail     = "notification_email"      // NotificationEmail 通知邮箱地址
+)
+
+var (
+	NotifyTypeEmail   = "email"   // Email 邮件
+	NotifyTypeWebhook = "webhook" // Webhook
+)