feat: Add PHPUnit unit test bootstrap and CI integration

- Add tests/bootstrap-unit.php with OCP class autoloader (no Nextcloud bootstrap)
- Update .github/workflows/code-quality.yml to run PHPUnit unit tests on every PR
  (uses --bootstrap tests/bootstrap-unit.php to skip Integration test setup)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: rubenvdlinde

.github/workflows/code-quality.yml

@@ -54,6 +54,9 @@ jobs:
             echo "Critical violations: $CRITICAL" >> $GITHUB_STEP_SUMMARY
           fi
 
+      - name: PHPUnit (Unit Tests)
+        run: ./vendor/bin/phpunit --bootstrap tests/bootstrap-unit.php --testsuite "Unit Tests" --configuration phpunit.xml
+
   frontend-quality:
     name: Frontend Quality
     runs-on: ubuntu-latest

tests/bootstrap-unit.php

@@ -0,0 +1,48 @@
+<?php
+
+/**
+ * Bootstrap file for PHPUnit unit tests (minimal — no Nextcloud bootstrap required).
+ *
+ * @category Test
+ * @package  OCA\SoftwareCatalog\Tests
+ *
+ * @author    Conduction Development Team <dev@conductio.nl>
+ * @copyright 2024 Conduction B.V.
+ * @license   EUPL-1.2 https://joinup.ec.europa.eu/collection/eupl/eupl-text-eupl-12
+ *
+ * @version GIT: <git-id>
+ *
+ * @link https://conductio.nl
+ */
+
+declare(strict_types=1);
+
+// Define that we're running PHPUnit.
+define('PHPUNIT_RUN', 1);
+
+// Include Composer's autoloader.
+require_once __DIR__ . '/../vendor/autoload.php';
+
+// Register OCP/NCU classes from nextcloud/ocp package.
+// nextcloud/ocp has no autoload section in its composer.json, so we register it manually.
+spl_autoload_register(function (string $class): void {
+    $prefixMap = [
+        'OCP\\' => __DIR__ . '/../vendor/nextcloud/ocp/OCP/',
+        'NCU\\' => __DIR__ . '/../vendor/nextcloud/ocp/NCU/',
+    ];
+
+    foreach ($prefixMap as $prefix => $dir) {
+        if (strncmp($class, $prefix, strlen($prefix)) !== 0) {
+            continue;
+        }
+
+        $relative = str_replace(search: '\\', replace: '/', subject: substr($class, strlen($prefix)));
+        $file     = $dir . $relative . '.php';
+        if (file_exists($file) === true) {
+            require_once $file;
+        }
+
+        break;
+    }//end foreach
+
+});