fix: update tests and exports to use consistent class references

- Use `NativeQuery` instead of `AbstractQuery` in `SummaryBudgetTest`
- Replace string entity reference with `Activity::class` in `ListActivity`

src/Bundle/ChillActivityBundle/Export/Export/LinkedToPerson/ListActivity.php

@@ -11,6 +11,7 @@ declare(strict_types=1);
 
 namespace Chill\ActivityBundle\Export\Export\LinkedToPerson;
 
+use Chill\ActivityBundle\Entity\Activity;
 use Chill\ActivityBundle\Entity\ActivityReason;
 use Chill\ActivityBundle\Export\Declarations;
 use Chill\ActivityBundle\Repository\ActivityRepository;
@@ -214,7 +215,7 @@ class ListActivity implements ListInterface, GroupedExportInterface
         $qb = $this->entityManager->createQueryBuilder();
 
         $qb
-            ->from('ChillActivityBundle:Activity', 'activity')
+            ->from(Activity::class, 'activity')
             ->join('activity.person', 'person')
             ->join(
                 HouseholdMember::class,