server: infer archive collected_at from source events

internal/server/handlers.go

@@ -1589,7 +1589,29 @@ func applyArchiveSourceMetadata(result *models.AnalysisResult) {
 	result.SourceType = models.SourceTypeArchive
 	result.Protocol = ""
 	result.TargetHost = ""
-	result.CollectedAt = time.Now().UTC()
+	if result.CollectedAt.IsZero() {
+		result.CollectedAt = inferArchiveCollectedAt(result)
+	}
+}
+
+func inferArchiveCollectedAt(result *models.AnalysisResult) time.Time {
+	if result == nil {
+		return time.Now().UTC()
+	}
+
+	var latest time.Time
+	for _, event := range result.Events {
+		if event.Timestamp.IsZero() {
+			continue
+		}
+		if latest.IsZero() || event.Timestamp.After(latest) {
+			latest = event.Timestamp
+		}
+	}
+	if !latest.IsZero() {
+		return latest.UTC()
+	}
+	return time.Now().UTC()
 }
 
 func applyCollectSourceMetadata(result *models.AnalysisResult, req CollectRequest) {

internal/server/source_metadata_test.go

@@ -30,6 +30,36 @@ func TestApplyArchiveSourceMetadata(t *testing.T) {
 	}
 }
 
+func TestApplyArchiveSourceMetadata_PreservesExistingCollectedAt(t *testing.T) {
+	expected := time.Date(2026, 2, 10, 15, 30, 0, 0, time.UTC)
+	result := &models.AnalysisResult{
+		CollectedAt: expected,
+	}
+
+	applyArchiveSourceMetadata(result)
+
+	if !result.CollectedAt.Equal(expected) {
+		t.Fatalf("expected collected_at to be preserved: got %s want %s", result.CollectedAt, expected)
+	}
+}
+
+func TestApplyArchiveSourceMetadata_InferCollectedAtFromEvents(t *testing.T) {
+	oldTs := time.Date(2026, 2, 10, 13, 0, 0, 0, time.UTC)
+	newTs := time.Date(2026, 2, 10, 15, 30, 0, 0, time.UTC)
+	result := &models.AnalysisResult{
+		Events: []models.Event{
+			{Timestamp: oldTs},
+			{Timestamp: newTs},
+		},
+	}
+
+	applyArchiveSourceMetadata(result)
+
+	if !result.CollectedAt.Equal(newTs) {
+		t.Fatalf("expected collected_at from latest event: got %s want %s", result.CollectedAt, newTs)
+	}
+}
+
 func TestApplyCollectSourceMetadata(t *testing.T) {
 	req := CollectRequest{
 		Host:     "bmc-api.local",