feat: Setup projet Classeo avec infrastructure Docker et architecture DDD

Configure l'environnement de développement complet avec Docker Compose,
structure DDD 4 Bounded Contexts, et pipeline CI/CD GitHub Actions.

Corrections compatibilité CI:
- Symfony 8 nécessite monolog-bundle ^4.0 (la v3.x ne supporte que jusqu'à Symfony 7)
- ESLint v9 nécessite flat config (eslint.config.js) - le format .eslintrc.cjs est obsolète

backend/tests/Unit/Shared/Domain/AggregateRootTest.php

@@ -0,0 +1,87 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Unit\Shared\Domain;
+
+use App\Shared\Domain\AggregateRoot;
+use App\Shared\Domain\DomainEvent;
+use DateTimeImmutable;
+use PHPUnit\Framework\TestCase;
+use Ramsey\Uuid\Uuid;
+use Ramsey\Uuid\UuidInterface;
+
+final class AggregateRootTest extends TestCase
+{
+    public function testPullDomainEventsReturnsRecordedEvents(): void
+    {
+        $aggregate = new TestAggregate();
+        $event1 = new TestDomainEvent('test1');
+        $event2 = new TestDomainEvent('test2');
+
+        $aggregate->doSomething($event1);
+        $aggregate->doSomething($event2);
+
+        $events = $aggregate->pullDomainEvents();
+
+        $this->assertCount(2, $events);
+        $this->assertSame($event1, $events[0]);
+        $this->assertSame($event2, $events[1]);
+    }
+
+    public function testPullDomainEventsClearsEventsAfterPulling(): void
+    {
+        $aggregate = new TestAggregate();
+        $event = new TestDomainEvent('test');
+
+        $aggregate->doSomething($event);
+        $aggregate->pullDomainEvents();
+
+        $secondPull = $aggregate->pullDomainEvents();
+
+        $this->assertCount(0, $secondPull);
+    }
+
+    public function testRecordEventAddsEventToInternalList(): void
+    {
+        $aggregate = new TestAggregate();
+        $event = new TestDomainEvent('test');
+
+        $aggregate->doSomething($event);
+        $events = $aggregate->pullDomainEvents();
+
+        $this->assertCount(1, $events);
+        $this->assertInstanceOf(TestDomainEvent::class, $events[0]);
+    }
+}
+
+// Test implementations
+final class TestAggregate extends AggregateRoot
+{
+    public function doSomething(DomainEvent $event): void
+    {
+        $this->recordEvent($event);
+    }
+}
+
+final readonly class TestDomainEvent implements DomainEvent
+{
+    private DateTimeImmutable $occurredOn;
+
+    public function __construct(
+        public string $data,
+        private ?UuidInterface $testAggregateId = null,
+    ) {
+        $this->occurredOn = new DateTimeImmutable();
+    }
+
+    public function occurredOn(): DateTimeImmutable
+    {
+        return $this->occurredOn;
+    }
+
+    public function aggregateId(): UuidInterface
+    {
+        return $this->testAggregateId ?? Uuid::uuid4();
+    }
+}