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.

src/Module/Mail/MailModule.php

@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Module\Mail;
+
+use App\Shared\Domain\Module\ModuleInterface;
+
+final class MailModule implements ModuleInterface
+{
+    public static function id(): string
+    {
+        return 'mail';
+    }
+
+    public static function label(): string
+    {
+        return 'Messagerie';
+    }
+
+    public static function isRequired(): bool
+    {
+        return false;
+    }
+
+    /**
+     * Permissions RBAC fin du Module Mail.
+     *
+     * Additif : alimente le catalogue RBAC. La sécurité des opérations API
+     * reste en ROLE_USER/ROLE_ADMIN (non recâblée ici).
+     *
+     * @return list<array{code: string, label: string}>
+     */
+    public static function permissions(): array
+    {
+        return [
+            ['code' => 'mail.access', 'label' => 'Accéder à la messagerie'],
+            ['code' => 'mail.configure', 'label' => 'Configurer la messagerie'],
+        ];
+    }
+}