feat(sites) : brique fondatrice du module Sites (ticket 1/4)

Module Sites optionnel et desactivable via config/modules.php.
Entite Site (nom unique, ville, CP FR, couleur hex, adresse),
repository + impl Doctrine, migration racine (namespace DoctrineMigrations
conforme exception CLAUDE.md), fixtures idempotentes (Chatellerault,
Saint-Jean, Pommevic), permissions RBAC sites.view/sites.manage.
Tests unitaires + validation via KernelTestCase (UniqueEntity, regex
hex et CP, NotBlank, Length).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Module/Sites/Domain/Repository/SiteRepositoryInterface.php

@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Module\Sites\Domain\Repository;
+
+use App\Module\Sites\Domain\Entity\Site;
+
+interface SiteRepositoryInterface
+{
+    public function findById(int $id): ?Site;
+
+    public function findByName(string $name): ?Site;
+
+    /**
+     * @return list<Site>
+     */
+    public function findAllOrderedByName(): array;
+
+    public function save(Site $site): void;
+
+    public function remove(Site $site): void;
+}