refactor(core) : RBAC Task 1 - polish apres revue qualite

- Permission : guards constructeur (code/label/module non vides, code avec point)
- Permission::revive() reutilise updateMetadata() pour eviter la duplication
- Suppression de SystemRolesTest (tautologique, ne capture aucun comportement)
- Role::permissions : commentaire explicite sur la raison du fetch EAGER
- Alignement des types de retour sur static (style User.php)
- Nouveau test Role::addPermission avec permissions distinctes

Ticket #343 - Task 1 polish (revue qualite).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/Module/Core/Domain/Entity/PermissionTest.php

@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace App\Tests\Module\Core\Domain\Entity;
 
 use App\Module\Core\Domain\Entity\Permission;
+use InvalidArgumentException;
 use PHPUnit\Framework\TestCase;
 
 /**
@@ -54,4 +55,33 @@ final class PermissionTest extends TestCase
         self::assertTrue($permission->isOrphan());
         self::assertSame('Lbl', $permission->getLabel());
     }
+
+    public function testConstructorRejectsEmptyCode(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+
+        new Permission('', 'Libelle', 'core');
+    }
+
+    public function testConstructorRejectsCodeWithoutDot(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('invalid_format');
+
+        new Permission('invalid_format', 'Libelle', 'core');
+    }
+
+    public function testConstructorRejectsEmptyLabel(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+
+        new Permission('core.users.view', '', 'core');
+    }
+
+    public function testConstructorRejectsEmptyModule(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+
+        new Permission('core.users.view', 'Libelle', '');
+    }
 }

tests/Module/Core/Domain/Entity/RoleTest.php

@@ -37,6 +37,18 @@ final class RoleTest extends TestCase
         self::assertSame(1, $role->getPermissions()->count());
     }
 
+    public function testAddPermissionAddsMultipleDistinct(): void
+    {
+        $role           = new Role('custom', 'Custom');
+        $permissionView = new Permission('core.users.view', 'Voir', 'core');
+        $permissionEdit = new Permission('core.users.edit', 'Editer', 'core');
+
+        $role->addPermission($permissionView);
+        $role->addPermission($permissionEdit);
+
+        self::assertSame(2, $role->getPermissions()->count());
+    }
+
     public function testRemovePermissionRemovesWhenPresent(): void
     {
         $role       = new Role('custom', 'Custom');