fix: address code review findings

internal/routing/graph.go

@@ -1108,7 +1108,7 @@ func (g *Graph) checkRouteForChanges(itinerary *Itinerary) bool {
 				}
 				// Check for significant delay (more than 2x normal duration)
 				if edge.Duration > leg.Duration*2 && leg.Duration > 0 {
-					if !needsReSearch || itinerary.ReSearchReason == string(reasonNone) {
+					if !needsReSearch {
 						needsReSearch = true
 						itinerary.NeedsReSearch = true
 						itinerary.ReSearchReason = string(reasonMajorDelay)
@@ -1131,8 +1131,8 @@ func (g *Graph) rescheduleRoute(originID, destID string, opts SearchOptions, clo
 	result := g.FindRoute(originID, destID, opts, closedStations, neighbors, yclient...)
 	if result != nil {
 		result.LastChecked = time.Now().Unix()
-		result.NeedsReSearch = false
-		result.ReSearchReason = string(reasonNone)
+		// Keep NeedsReSearch and ReSearchReason from the original itinerary to indicate
+		// that a re-search was triggered due to changes
 	}
 	return result
 }
@@ -1141,7 +1141,13 @@ func (g *Graph) rescheduleRoute(originID, destID string, opts SearchOptions, clo
 // This is the main entry point for flight change notification logic.
 func (g *Graph) CheckAndRescheduleRoute(itinerary *Itinerary, originID, destID string, opts SearchOptions, closedStations map[string]bool, neighbors map[string][]storage.StationNeighbor, yclient ...*yandex.Client) *Itinerary {
 	if g.checkRouteForChanges(itinerary) {
-		return g.rescheduleRoute(originID, destID, opts, closedStations, neighbors, yclient...)
+		result := g.rescheduleRoute(originID, destID, opts, closedStations, neighbors, yclient...)
+		if result != nil {
+			// Preserve the NeedsReSearch and ReSearchReason from the original itinerary
+			result.NeedsReSearch = itinerary.NeedsReSearch
+			result.ReSearchReason = itinerary.ReSearchReason
+		}
+		return result
 	}
 	return itinerary
 }