preserve schedule start date

backend/app/Schedule/EloquentScheduleRepository.php

@@ -52,7 +52,6 @@ class EloquentScheduleRepository implements ScheduleRepository
                 );
             }
 
-            $model->start_date = $dto->startDate->format('Y-m-d');
             $model->target_date = $dto->targetDate->format('Y-m-d');
             $model->save();
 

backend/app/Schedule/RescheduleScheduleDto.php

@@ -13,7 +13,6 @@ final readonly class RescheduleScheduleDto
     public function __construct(
         public int $scheduleId,
         public User $user,
-        public DateTimeImmutable $startDate,
         public DateTimeImmutable $targetDate,
         public array $assignments,
     ) {}

backend/app/Schedule/UseCases/RescheduleSchedule/RescheduleSchedule.php

@@ -75,7 +75,6 @@ class RescheduleSchedule
             new RescheduleScheduleDto(
                 scheduleId: $schedule->getId(),
                 user: $request->user,
-                startDate: $startDate,
                 targetDate: $targetDate,
                 assignments: $assignmentDtos,
             ),

backend/tests/Fakes/FakeScheduleRepository.php

@@ -87,7 +87,7 @@ class FakeScheduleRepository implements ScheduleRepository
             user: $schedule->getUser(),
             setName: $schedule->getSetName(),
             elementKind: $schedule->getElementKind(),
-            startDate: $dto->startDate,
+            startDate: $schedule->getStartDate(),
             targetDate: $dto->targetDate,
             assignments: $assignments,
         );