feat: 添加通知管理功能，包括服务层逻辑和HTTP API处理。

internal/handler/notification_handler.go

@@ -185,10 +185,31 @@ func (h *NotificationHandler) DeleteNotification(c *gin.Context) {
 	api.NoContent(c)
 }
 
+// CreateNotification handles POST /api/v1/notifications
+// Creates a new notification (Admin/System use)
+func (h *NotificationHandler) CreateNotification(c *gin.Context) {
+	// TODO: Add admin authorization check
+
+	var input service.CreateNotificationInput
+	if err := c.ShouldBindJSON(&input); err != nil {
+		api.BadRequest(c, "Invalid request body: "+err.Error())
+		return
+	}
+
+	notification, err := h.notificationService.CreateNotification(input)
+	if err != nil {
+		api.InternalError(c, "Failed to create notification: "+err.Error())
+		return
+	}
+
+	api.Created(c, notification)
+}
+
 // RegisterRoutes registers all notification routes to the given router group
 func (h *NotificationHandler) RegisterRoutes(rg *gin.RouterGroup) {
 	notifications := rg.Group("/notifications")
 	{
+		notifications.POST("", h.CreateNotification)
 		notifications.GET("", h.GetNotifications)
 		notifications.GET("/unread-count", h.GetUnreadCount)
 		notifications.PUT("/:id/read", h.MarkAsRead)