feat: enable entering additional remarks in offer confirmation

src/Controller/Groups/OfferController.php

@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace App\Controller\Groups;
 
 use App\Entity\Groups\AccommodationBooking;
+use App\Form\Model\OfferAcceptDto;
 use App\Form\OfferAcceptConfirmationType;
 use App\Htmx\HxTrait;
 use App\Model\AccommodationBookingContext;
@@ -97,13 +98,16 @@ class OfferController extends AbstractController
             return $this->redirectToOfferPage($request, $uuid);
         }
 
-        $confirmationForm = $this->createForm(OfferAcceptConfirmationType::class, null, [
+        $dto = new OfferAcceptDto(remarks: $booking->getRemarks());
+        $confirmationForm = $this->createForm(OfferAcceptConfirmationType::class, $dto, [
             'terms_url' => $this->termsUrlProvider->forAccommodation($booking->getAccommodation()),
         ]);
         $confirmationForm->handleRequest($request);
 
         if ($confirmationForm->isSubmitted() && $confirmationForm->isValid()) {
-            $this->bookingService->acceptBooking($booking);
+            // The textarea is prefilled, so the submitted value is the complete remark —
+            // an emptied field arrives as null and must clear the stored one, not keep it.
+            $this->bookingService->acceptBooking($booking, $dto->remarks ?? '');
             $this->addFlash('success', 'Deine Buchung ist bestätigt.');
 
             return $this->redirectToOfferPage($request, $uuid);