chore: fix phpstan errors

src/BusProNet/DataProcessor/ServiceMappingCollector.php

@@ -20,7 +20,7 @@ class ServiceMappingCollector
      *
      * Groups participants by their assigned room ID.
      *
-     * @return array<string, array<int>> Map of room ID to participant IDs
+     * @return array<int, list<int>> Map of room ID to participant IDs
      */
     public function collectRoomMappings(BookingDto $bookingDto): array
     {