feat: Messaging asynchrone fiable avec retry, dead-letter et métriques

Les événements métier (emails d'invitation, reset password, activation)
bloquaient la réponse API en étant traités de manière synchrone. Ce commit
route ces événements vers un transport AMQP asynchrone avec un worker
dédié, garantissant des réponses API rapides et une gestion robuste des
échecs.

Le retry utilise une stratégie Fibonacci (1s, 1s, 2s, 3s, 5s, 8s, 13s)
qui offre un bon compromis entre réactivité et protection des services
externes. Les messages qui épuisent leurs tentatives arrivent dans une
dead-letter queue Doctrine avec alerte email à l'admin.

La commande console CreateTestActivationTokenCommand détecte désormais
les comptes déjà actifs et génère un token de réinitialisation de mot
de passe au lieu d'un token d'activation, évitant une erreur bloquante
lors de la ré-invitation par un admin.

backend/tests/Unit/Shared/Infrastructure/Messenger/MessengerMetricsMiddlewareTest.php

@@ -0,0 +1,165 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Unit\Shared\Infrastructure\Messenger;
+
+use App\Shared\Infrastructure\Messenger\MessengerMetricsMiddleware;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+use Prometheus\CollectorRegistry;
+use Prometheus\Counter;
+use RuntimeException;
+use stdClass;
+use Symfony\Component\Messenger\Envelope;
+use Symfony\Component\Messenger\Middleware\MiddlewareInterface;
+use Symfony\Component\Messenger\Middleware\StackInterface;
+use Symfony\Component\Messenger\Stamp\HandledStamp;
+
+final class MessengerMetricsMiddlewareTest extends TestCase
+{
+    #[Test]
+    public function itIncrementsHandledCounterOnSuccess(): void
+    {
+        $handledCounter = $this->createMock(Counter::class);
+        $failedCounter = $this->createMock(Counter::class);
+
+        // Label is now the message class name, not the handler name
+        $handledCounter->expects($this->once())
+            ->method('inc')
+            ->with(['stdClass']);
+
+        $failedCounter->expects($this->never())->method('inc');
+
+        $registry = $this->createRegistryMock($handledCounter, $failedCounter);
+        $middleware = new MessengerMetricsMiddleware($registry);
+
+        $envelope = new Envelope(new stdClass());
+        $returnedEnvelope = $envelope->with(new HandledStamp('result', 'App\\Test\\TestHandler'));
+
+        $stack = $this->createStackReturning($returnedEnvelope);
+
+        $middleware->handle($envelope, $stack);
+    }
+
+    #[Test]
+    public function itIncrementsFailedCounterOnException(): void
+    {
+        $handledCounter = $this->createMock(Counter::class);
+        $failedCounter = $this->createMock(Counter::class);
+
+        $handledCounter->expects($this->never())->method('inc');
+        $failedCounter->expects($this->once())
+            ->method('inc')
+            ->with(['stdClass']);
+
+        $registry = $this->createRegistryMock($handledCounter, $failedCounter);
+        $middleware = new MessengerMetricsMiddleware($registry);
+
+        $envelope = new Envelope(new stdClass());
+        $stack = $this->createStackThrowing(new RuntimeException('fail'));
+
+        $this->expectException(RuntimeException::class);
+        $middleware->handle($envelope, $stack);
+    }
+
+    #[Test]
+    public function itDoesNotIncrementHandledWhenNoHandledStamps(): void
+    {
+        $handledCounter = $this->createMock(Counter::class);
+        $failedCounter = $this->createMock(Counter::class);
+
+        $handledCounter->expects($this->never())->method('inc');
+        $failedCounter->expects($this->never())->method('inc');
+
+        $registry = $this->createRegistryMock($handledCounter, $failedCounter);
+        $middleware = new MessengerMetricsMiddleware($registry);
+
+        // No HandledStamp = async dispatch, no handler executed yet
+        $envelope = new Envelope(new stdClass());
+        $stack = $this->createStackReturning($envelope);
+
+        $middleware->handle($envelope, $stack);
+    }
+
+    #[Test]
+    public function itSurvivesPrometheusStorageFailure(): void
+    {
+        $handledCounter = $this->createMock(Counter::class);
+        $failedCounter = $this->createMock(Counter::class);
+
+        // Simulate Redis/Prometheus failure
+        $handledCounter->method('inc')->willThrowException(new RuntimeException('Redis connection refused'));
+
+        $registry = $this->createRegistryMock($handledCounter, $failedCounter);
+        $middleware = new MessengerMetricsMiddleware($registry);
+
+        $envelope = new Envelope(new stdClass());
+        $returnedEnvelope = $envelope->with(new HandledStamp('result', 'App\\Test\\TestHandler'));
+        $stack = $this->createStackReturning($returnedEnvelope);
+
+        // Should NOT throw - metrics failure is swallowed
+        $result = $middleware->handle($envelope, $stack);
+        self::assertSame($returnedEnvelope, $result);
+    }
+
+    private function createRegistryMock(Counter $handledCounter, Counter $failedCounter): CollectorRegistry
+    {
+        $registry = $this->createMock(CollectorRegistry::class);
+        $registry->method('getOrRegisterCounter')
+            ->willReturnCallback(
+                static fn (string $ns, string $name): Counter => match (true) {
+                    str_contains($name, 'handled') => $handledCounter,
+                    str_contains($name, 'failed') => $failedCounter,
+                },
+            );
+
+        return $registry;
+    }
+
+    private function createStackReturning(Envelope $envelope): StackInterface
+    {
+        return new class($envelope) implements StackInterface {
+            public function __construct(private readonly Envelope $envelope)
+            {
+            }
+
+            public function next(): MiddlewareInterface
+            {
+                return new class($this->envelope) implements MiddlewareInterface {
+                    public function __construct(private readonly Envelope $envelope)
+                    {
+                    }
+
+                    public function handle(Envelope $envelope, StackInterface $stack): Envelope
+                    {
+                        return $this->envelope;
+                    }
+                };
+            }
+        };
+    }
+
+    private function createStackThrowing(RuntimeException $exception): StackInterface
+    {
+        return new class($exception) implements StackInterface {
+            public function __construct(private readonly RuntimeException $exception)
+            {
+            }
+
+            public function next(): MiddlewareInterface
+            {
+                return new class($this->exception) implements MiddlewareInterface {
+                    public function __construct(private readonly RuntimeException $exception)
+                    {
+                    }
+
+                    public function handle(Envelope $envelope, StackInterface $stack): Envelope
+                    {
+                        throw $this->exception;
+                    }
+                };
+            }
+        };
+    }
+}