fix: code correctness, security, and simplicity improvements

internal/routing/graph.go

@@ -253,11 +253,11 @@ func (g *Graph) FindRoute(originID, destID string, opts SearchOptions) *Itinerar
 
 			newDurationWithMCT := newDuration + transferTime
 
-			// Check if we've visited this node with fewer or equal transfers
+			// Check if we've visited this node with fewer transfers
 			visKey := current.nodeID
 			if existingTransfers, ok := visited[visKey]; ok {
-				if current.transfers+1 >= existingTransfers {
-					// Already visited this node with fewer or equal transfers, skip
+				if current.transfers+1 > existingTransfers {
+					// Already visited this node with fewer transfers, skip
 					continue
 				}
 			}