refactor(domain): Reorganize aggregates into dedicated namespace structure

src/Application/Handlers/RegisterCarrierHandler.php

@@ -3,7 +3,7 @@
 namespace DistributingCarriers\Application\Handlers;
 
 use DistributingCarriers\Application\Commands\RegisterCarrierCommand;
-use DistributingCarriers\Domain\Carrier;
+use DistributingCarriers\Domain\Aggregates\Carrier;
 use DistributingCarriers\Infrastructure\EventSourcing\EventStore;
 
 class RegisterCarrierHandler
@@ -23,6 +23,6 @@ class RegisterCarrierHandler
         $this->eventStore->save($carrier->getId(), $carrier->getUncommittedChanges(), $carrier->getVersion());
         $carrier->markChangesAsCommitted();
 
-        echo "Carrier registered with ID: " . $carrierId . "\n";
+        echo "Carrier registered with ID: $carrierId\n";
     }
 }

src/Domain/Aggregates/AggregateRoot.php

@@ -1,6 +1,6 @@
 <?php
 
-namespace DistributingCarriers\Domain;
+namespace DistributingCarriers\Domain\Aggregates;
 
 abstract class AggregateRoot
 {

src/Domain/Aggregates/Carrier.php

@@ -1,6 +1,6 @@
 <?php
 
-namespace DistributingCarriers\Domain;
+namespace DistributingCarriers\Domain\Aggregates;
 
 use DistributingCarriers\Domain\Events\CarrierRegistered;