feat: Gestion des classes scolaires

Permet aux administrateurs de créer, modifier et supprimer des classes
pour organiser les élèves par niveau. L'archivage soft-delete préserve
l'historique tout en masquant les classes obsolètes.

Inclut la validation des noms (2-50 caractères), les niveaux scolaires
du CP à la Terminale, et les contrôles d'accès par rôle.

backend/src/Administration/Infrastructure/Persistence/InMemory/InMemoryClassRepository.php

@@ -0,0 +1,100 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Administration\Infrastructure\Persistence\InMemory;
+
+use App\Administration\Domain\Exception\ClasseNotFoundException;
+use App\Administration\Domain\Model\SchoolClass\AcademicYearId;
+use App\Administration\Domain\Model\SchoolClass\ClassId;
+use App\Administration\Domain\Model\SchoolClass\ClassName;
+use App\Administration\Domain\Model\SchoolClass\ClassStatus;
+use App\Administration\Domain\Model\SchoolClass\SchoolClass;
+use App\Administration\Domain\Repository\ClassRepository;
+use App\Shared\Domain\Tenant\TenantId;
+use Override;
+
+final class InMemoryClassRepository implements ClassRepository
+{
+    /** @var array<string, SchoolClass> Indexed by ID */
+    private array $byId = [];
+
+    /** @var array<string, SchoolClass> Indexed by tenant:year:name */
+    private array $byTenantYearName = [];
+
+    #[Override]
+    public function save(SchoolClass $class): void
+    {
+        // If class already exists, remove the old name key (handles renames)
+        $existingClass = $this->byId[(string) $class->id] ?? null;
+        if ($existingClass !== null) {
+            $oldKey = $this->nameKey($existingClass->name, $existingClass->tenantId, $existingClass->academicYearId);
+            unset($this->byTenantYearName[$oldKey]);
+        }
+
+        $this->byId[(string) $class->id] = $class;
+        $this->byTenantYearName[$this->nameKey($class->name, $class->tenantId, $class->academicYearId)] = $class;
+    }
+
+    #[Override]
+    public function get(ClassId $id): SchoolClass
+    {
+        $class = $this->findById($id);
+
+        if ($class === null) {
+            throw ClasseNotFoundException::withId($id);
+        }
+
+        return $class;
+    }
+
+    #[Override]
+    public function findById(ClassId $id): ?SchoolClass
+    {
+        return $this->byId[(string) $id] ?? null;
+    }
+
+    #[Override]
+    public function findByName(
+        ClassName $name,
+        TenantId $tenantId,
+        AcademicYearId $academicYearId,
+    ): ?SchoolClass {
+        return $this->byTenantYearName[$this->nameKey($name, $tenantId, $academicYearId)] ?? null;
+    }
+
+    #[Override]
+    public function findActiveByTenantAndYear(
+        TenantId $tenantId,
+        AcademicYearId $academicYearId,
+    ): array {
+        $result = [];
+
+        foreach ($this->byId as $class) {
+            if ($class->tenantId->equals($tenantId)
+                && $class->academicYearId->equals($academicYearId)
+                && $class->status === ClassStatus::ACTIVE
+            ) {
+                $result[] = $class;
+            }
+        }
+
+        return $result;
+    }
+
+    #[Override]
+    public function delete(ClassId $id): void
+    {
+        $class = $this->byId[(string) $id] ?? null;
+
+        if ($class !== null) {
+            unset($this->byId[(string) $id]);
+            unset($this->byTenantYearName[$this->nameKey($class->name, $class->tenantId, $class->academicYearId)]);
+        }
+    }
+
+    private function nameKey(ClassName $name, TenantId $tenantId, AcademicYearId $academicYearId): string
+    {
+        return $tenantId . ':' . $academicYearId . ':' . mb_strtolower((string) $name, 'UTF-8');
+    }
+}