Let plugins run their own PHP code

A plugin can now bring a plugin.php that registers hooks, scheduled tasks, its own tables, public pages and admin screens. Failures stay contained to the plugin; a form on a plugin page can be submitted.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/Controller/SeoController.php

@@ -17,7 +17,7 @@ use Symfony\Component\Routing\Attribute\Route;
  */
 final class SeoController extends AbstractController
 {
-    public function __construct(
+    public function __construct(private \App\Plugin\PluginRuntime $plugins,
         private Connection $db,
         private SiteSettings $settings,
         private PostRepository $posts,
@@ -74,6 +74,8 @@ final class SeoController extends AbstractController
             $entries[] = ['loc' => $origin.'/'.PostRepository::ARCHIVE_PREFIX[$row['kind']].'/'.$row['slug'], 'lastmod' => null];
         }
 
+        $entries = $this->plugins->applyFilters('sitemap.entries', $entries, $origin);
+
         return $this->xml($this->renderView('seo/sitemap.xml.twig', ['entries' => $entries]));
     }