fix(documents) : add serialization groups to prevent OOM on collection endpoint

The path field (base64 data URIs) is now excluded from GetCollection
via document:list group. Individual GET returns path via document:detail
group. Related entities expose id+name in document:list for attachment
display. Frontend lazy-loads path on download/preview click.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/Entity/Site.php

@@ -16,6 +16,7 @@ use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\Common\Collections\Collection;
 use Doctrine\DBAL\Types\Types;
 use Doctrine\ORM\Mapping as ORM;
+use Symfony\Component\Serializer\Attribute\Groups;
 use Symfony\Component\Validator\Constraints as Assert;
 
 #[ORM\Entity(repositoryClass: SiteRepository::class)]
@@ -36,10 +37,12 @@ class Site
 {
     #[ORM\Id]
     #[ORM\Column(type: Types::STRING, length: 36)]
+    #[Groups(['document:list'])]
     private ?string $id = null;
 
     #[ORM\Column(type: Types::STRING, length: 255)]
     #[Assert\NotBlank]
+    #[Groups(['document:list'])]
     private string $name;
 
     #[ORM\Column(type: Types::STRING, length: 255, options: ['default' => ''], name: 'contactName')]