feat: 网络双线图+告警联系人/联系组+Agent v2.0.0 + 一键报警阈值

- HostMonitor: 网络改为双线图 rx/tx 网卡带宽吞吐(双Area线), 移除单rx图
- Agent: 默认版本号从 dev 改为 v2.0.0, 重建二进制 5.2MB
- 告警中心: 新增报警联系人/报警联系组 Tab, ContactDialog/ContactGroupDialog
- 后端: AlertContact/AlertContactGroup 模型+CRUD, monitor_alert_contacts/groups 表
- 路由: /alerts/contacts + /alerts/contact-groups 8个REST端点
- 一键报警: 更新描述为6条规则(含TCP+进程), 切换到 /alerts/quick-setup
- 测试规则: 内存>10% 触发告警已创建, 飞书通知验证通过

backend/internal/api/routes/routes.go

@@ -455,6 +455,16 @@ func Register(r *gin.Engine, db *gorm.DB, log *zap.Logger, cfg *config.Config, c
 		alerts.DELETE("/notify-channels/:id", alertHandler.DeleteNotifyChannel)
 		alerts.POST("/notify-channels/:id/test", alertHandler.TestNotifyChannel)
 		alerts.POST("/quick-setup", alertHandler.QuickSetupRules)
+		// 报警联系人
+		alerts.GET("/contacts", alertHandler.ListContacts)
+		alerts.POST("/contacts", alertHandler.CreateContact)
+		alerts.PUT("/contacts/:id", alertHandler.UpdateContact)
+		alerts.DELETE("/contacts/:id", alertHandler.DeleteContact)
+		// 报警联系组
+		alerts.GET("/contact-groups", alertHandler.ListContactGroups)
+		alerts.POST("/contact-groups", alertHandler.CreateContactGroup)
+		alerts.PUT("/contact-groups/:id", alertHandler.UpdateContactGroup)
+		alerts.DELETE("/contact-groups/:id", alertHandler.DeleteContactGroup)
 	}
 
 	// 流水线路由