Use std::optional instead of sentinel values for absent data

src/lib/ecs/system/ai/DeliverScrapEvaluator.cpp

@@ -31,7 +31,7 @@ void DeliverScrapEvaluator::evaluate(EntityAdmin& admin, const BuildingSystem& b
             }
 
             // Assign nearest SalvageBay if not yet assigned.
-            if (deliver.deliveryBay == kInvalidBuildingId)
+            if (!deliver.deliveryBay.has_value())
             {
                 const Building* bay =
                     buildings.findNearestBuilding(pos.value, BuildingType::SalvageBay);