feat: 引入循环交易管理、邮件通知和用户设置功能

internal/handler/settings_handler.go

@@ -3,8 +3,8 @@ package handler
 import (
 	"errors"
 
-	"accounting-app/pkg/api"
 	"accounting-app/internal/service"
+	"accounting-app/pkg/api"
 
 	"github.com/gin-gonic/gin"
 )
@@ -70,6 +70,10 @@ func (h *SettingsHandler) UpdateSettings(c *gin.Context) {
 			api.BadRequest(c, "Invalid image compression, must be one of: low, medium, high")
 			return
 		}
+		if errors.Is(err, service.ErrInvalidNotificationChannel) {
+			api.BadRequest(c, "Invalid notification channel")
+			return
+		}
 		api.InternalError(c, "Failed to update settings: "+err.Error())
 		return
 	}