feat: add 24-hour traffic and capacity trend charts to dashboard and node detail pages

- Implemented TrendChart component for visualizing traffic and capacity trends.
- Enhanced DashboardOverview and NodeDetailPage components to display 24-hour request and capacity trends.
- Updated types to include traffic and capacity trend data structures.
- Created observability trends service to aggregate traffic and capacity data.
- Added tests for traffic report generation and trend data handling.
- Introduced new dependencies for charting (echarts and echarts-for-react).

atsf_server/model/node_health_event.go

@@ -35,3 +35,8 @@ func ListNodeHealthEvents(nodeID string, activeOnly bool, limit int) (events []*
 	err = query.Find(&events).Error
 	return events, err
 }
+
+func ListActiveNodeHealthEvents() (events []*NodeHealthEvent, err error) {
+	err = DB.Where("status = ?", "active").Order("last_triggered_at desc").Find(&events).Error
+	return events, err
+}