feat(dashboard): enhance dashboard overview and world stage components

- Implemented normalization for dashboard overview data to handle null or undefined values.
- Added ECharts map integration for visualizing node data on a world map.
- Introduced loading and error states for the map component.
- Updated UI components to support dark and light themes.
- Enhanced testing for dashboard overview to cover empty states and data fetching.
- Added type definitions for echarts-maps module.
- Updated package dependencies to include echarts-maps.

atsf_server/service/dashboard.go

@@ -160,6 +160,7 @@ func GetDashboardOverview() (*DashboardOverviewView, error) {
 	view := &DashboardOverviewView{
 		GeneratedAt:   now,
 		Nodes:         make([]DashboardNodeHealth, 0, len(nodes)),
+		ActiveAlerts:  make([]DashboardAlert, 0),
 		Distributions: buildTrafficDistributions(reports, 8),
 		Trends: DashboardTrends{
 			Traffic24h:  buildTrafficTrendPoints(now, reports),

atsf_server/service/node_update_test.go

@@ -879,3 +879,18 @@ func TestGetDashboardOverview(t *testing.T) {
 		t.Fatalf("unexpected riskiest node: %+v", view.Peaks.RiskiestNode)
 	}
 }
+
+func TestGetDashboardOverviewReturnsEmptyAlertSlice(t *testing.T) {
+	setupServiceTestDB(t)
+
+	view, err := GetDashboardOverview()
+	if err != nil {
+		t.Fatalf("GetDashboardOverview failed: %v", err)
+	}
+	if view.ActiveAlerts == nil {
+		t.Fatalf("expected active alerts to be an empty slice, got nil")
+	}
+	if len(view.ActiveAlerts) != 0 {
+		t.Fatalf("expected empty active alerts, got %+v", view.ActiveAlerts)
+	}
+}