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/service/observability_trends.go

@@ -0,0 +1,106 @@
+package service
+
+import (
+	"atsflare/model"
+	"time"
+)
+
+const observabilityTrendBuckets = 24
+
+type TrafficTrendPoint struct {
+	BucketStartedAt    time.Time `json:"bucket_started_at"`
+	RequestCount       int64     `json:"request_count"`
+	ErrorCount         int64     `json:"error_count"`
+	UniqueVisitorCount int64     `json:"unique_visitor_count"`
+}
+
+type CapacityTrendPoint struct {
+	BucketStartedAt           time.Time `json:"bucket_started_at"`
+	AverageCPUUsagePercent    float64   `json:"average_cpu_usage_percent"`
+	AverageMemoryUsagePercent float64   `json:"average_memory_usage_percent"`
+	ReportedNodes             int       `json:"reported_nodes"`
+}
+
+type capacityTrendAccumulator struct {
+	cpuSum   float64
+	cpuCount int
+	memSum   float64
+	memCount int
+	nodes    map[string]struct{}
+}
+
+func buildTrafficTrendPoints(now time.Time, reports []*model.NodeRequestReport) []TrafficTrendPoint {
+	start := trendWindowStart(now)
+	points := make([]TrafficTrendPoint, observabilityTrendBuckets)
+	for index := range points {
+		points[index].BucketStartedAt = start.Add(time.Duration(index) * time.Hour)
+	}
+
+	for _, report := range reports {
+		index, ok := trendBucketIndex(report.WindowEndedAt, start)
+		if !ok {
+			continue
+		}
+		points[index].RequestCount += report.RequestCount
+		points[index].ErrorCount += report.ErrorCount
+		points[index].UniqueVisitorCount += report.UniqueVisitorCount
+	}
+
+	return points
+}
+
+func buildCapacityTrendPoints(now time.Time, snapshots []*model.NodeMetricSnapshot) []CapacityTrendPoint {
+	start := trendWindowStart(now)
+	points := make([]CapacityTrendPoint, observabilityTrendBuckets)
+	accumulators := make([]capacityTrendAccumulator, observabilityTrendBuckets)
+	for index := range points {
+		points[index].BucketStartedAt = start.Add(time.Duration(index) * time.Hour)
+		accumulators[index].nodes = make(map[string]struct{})
+	}
+
+	for _, snapshot := range snapshots {
+		index, ok := trendBucketIndex(snapshot.CapturedAt, start)
+		if !ok {
+			continue
+		}
+		if snapshot.CPUUsagePercent > 0 {
+			accumulators[index].cpuSum += snapshot.CPUUsagePercent
+			accumulators[index].cpuCount++
+		}
+		if memoryUsage := percentage(snapshot.MemoryUsedBytes, snapshot.MemoryTotalBytes); memoryUsage > 0 {
+			accumulators[index].memSum += memoryUsage
+			accumulators[index].memCount++
+		}
+		if snapshot.NodeID != "" {
+			accumulators[index].nodes[snapshot.NodeID] = struct{}{}
+		}
+	}
+
+	for index := range points {
+		if accumulators[index].cpuCount > 0 {
+			points[index].AverageCPUUsagePercent = accumulators[index].cpuSum / float64(accumulators[index].cpuCount)
+		}
+		if accumulators[index].memCount > 0 {
+			points[index].AverageMemoryUsagePercent = accumulators[index].memSum / float64(accumulators[index].memCount)
+		}
+		points[index].ReportedNodes = len(accumulators[index].nodes)
+	}
+
+	return points
+}
+
+func trendWindowStart(now time.Time) time.Time {
+	return now.Truncate(time.Hour).Add(-(observabilityTrendBuckets - 1) * time.Hour)
+}
+
+func trendBucketIndex(timestamp time.Time, start time.Time) (int, bool) {
+	if timestamp.Before(start) {
+		return 0, false
+	}
+	delta := timestamp.Sub(start)
+	index := int(delta / time.Hour)
+	if index < 0 || index >= observabilityTrendBuckets {
+		return 0, false
+	}
+	return index, true
+}