feat: 添加通知管理功能，包括服务层逻辑和HTTP API处理。

internal/service/notification_service.go

@@ -25,11 +25,11 @@ func NewNotificationService(repo *repository.NotificationRepository) *Notificati
 
 // CreateNotificationInput represents input for creating a notification
 type CreateNotificationInput struct {
-	UserID    uint
-	Type      models.NotificationType
-	Title     string
-	Content   string
-	RelatedID *uint
+	UserID    uint                    `json:"user_id" binding:"required"`
+	Type      models.NotificationType `json:"type" binding:"required"`
+	Title     string                  `json:"title" binding:"required"`
+	Content   string                  `json:"content" binding:"required"`
+	RelatedID *uint                   `json:"related_id"`
 }
 
 // CreateNotification creates a new notification