chore: add SPDX header

Signed-off-by: Vitor Mattos <[email protected]>

Author: vitormattos

tests/php/Unit/Service/File/PdfValidatorTest.php

@@ -1,6 +1,10 @@
 <?php
 
 declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2025 LibreCode coop and contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
 
 namespace OCA\Libresign\Tests\Unit\Service\File;