feat(mail) : migrate Mail integration into module (back)

LST-67 (2.5) backend. Behaviour-preserving move of the IMAP mail integration
into src/Module/Mail/. All /api/mail/* routes, securities (ROLE_CLIENT still
excluded via MailAccessChecker) and the async sync are unchanged.

- 4 entities + 4 repositories (Domain interfaces + Doctrine impls, bound).
  TaskMailLink.task now references TaskInterface (contract) instead of the
  concrete PM Task. Link/unlink/list-mails controllers load tasks via
  TaskRepositoryInterface; MailCreateTaskController keeps the concrete Task
  (instantiation) — documented Mail->PM coupling.
- Domain (MailProviderInterface, exception), Application (5 DTOs, MailSyncService,
  MailSyncRequested message + handler), Infrastructure (ImapMailProvider +
  MimeHeaderDecoder, MailAccessChecker, 2 console commands, 12 controllers,
  ApiPlatform state + MailSettings resource). TokenEncryptor stays shared.
- doctrine mapping Mail; messenger routing repointed; services.yaml repo +
  provider bindings; MailModule registered (id mail, mail.access/configure).
- #[Auditable] + Timestampable on MailConfiguration only (additive migration);
  IMAP data entities keep their own sync timestamps.

163 tests green, mapping valid, no route regression, cs-fixer clean.

tests/Unit/Repository/MailConfigurationRepositoryTest.php

@@ -4,8 +4,8 @@ declare(strict_types=1);
 
 namespace App\Tests\Unit\Repository;
 
-use App\Entity\MailConfiguration;
-use App\Repository\MailConfigurationRepository;
+use App\Module\Mail\Domain\Entity\MailConfiguration;
+use App\Module\Mail\Infrastructure\Doctrine\DoctrineMailConfigurationRepository;
 use Doctrine\ORM\EntityManagerInterface;
 use Symfony\Bundle\FrameworkBundle\Test\KernelTestCase;
 
@@ -14,14 +14,14 @@ use Symfony\Bundle\FrameworkBundle\Test\KernelTestCase;
  */
 class MailConfigurationRepositoryTest extends KernelTestCase
 {
-    private MailConfigurationRepository $repository;
+    private DoctrineMailConfigurationRepository $repository;
     private EntityManagerInterface $em;
 
     protected function setUp(): void
     {
         self::bootKernel();
         $container        = static::getContainer();
-        $this->repository = $container->get(MailConfigurationRepository::class);
+        $this->repository = $container->get(DoctrineMailConfigurationRepository::class);
         $this->em         = $container->get('doctrine.orm.entity_manager');
         $this->em->getConnection()->executeStatement('TRUNCATE TABLE mail_configuration RESTART IDENTITY CASCADE');
     }