fix(composant) : replace unique constraint from name to reference validation

Remove DB unique index on composants.name and add Symfony UniqueEntity
validation on reference field with explicit error message.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Entity/Composant.php

@@ -23,8 +23,10 @@ use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\Common\Collections\Collection;
 use Doctrine\DBAL\Types\Types;
 use Doctrine\ORM\Mapping as ORM;
+use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;
 use Symfony\Component\Serializer\Attribute\Groups;
 
+#[UniqueEntity(fields: ['reference'], message: 'Un composant avec cette référence existe déjà.')]
 #[ORM\Entity(repositoryClass: ComposantRepository::class)]
 #[ORM\Table(name: 'composants')]
 #[ORM\HasLifecycleCallbacks]
@@ -54,7 +56,7 @@ class Composant
     #[Groups(['composant:read', 'document:list'])]
     private ?string $id = null;
 
-    #[ORM\Column(type: Types::STRING, length: 255, unique: true)]
+    #[ORM\Column(type: Types::STRING, length: 255)]
     #[Groups(['composant:read', 'document:list'])]
     private string $name;