refactor: Cleanup git state - commit all staged changes

Major refactoring cleanup:
- Add new controller architecture (class-controller-*.php)
- Add new settings-v2 UI (views/settings-v2/)
- Add new CSS architecture (agentic-sidebar.css, tokens)
- Add esbuild build pipeline (scripts/build.js, package.json)
- Add composer dependencies (vendor/)
- Add frontend src directory (assets/js/src/index.jsx)
- Add documentation files
- Remove old/obsolete files (class-settings.php, old CSS)

This commits all pending changes from previous refactoring efforts.

vendor/symfony/config/Resource/SelfCheckingResourceChecker.php

@@ -0,0 +1,46 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Config\Resource;
+
+use Symfony\Component\Config\ResourceCheckerInterface;
+
+/**
+ * Resource checker for instances of SelfCheckingResourceInterface.
+ *
+ * As these resources perform the actual check themselves, we can provide
+ * this class as a standard way of validating them.
+ *
+ * @author Matthias Pigulla <mp@webfactory.de>
+ */
+class SelfCheckingResourceChecker implements ResourceCheckerInterface
+{
+    // Common shared cache, because this checker can be used in different
+    // situations. For example, when using the full stack framework, the router
+    // and the container have their own cache. But they may check the very same
+    // resources
+    private static array $cache = [];
+
+    public function supports(ResourceInterface $metadata): bool
+    {
+        return $metadata instanceof SelfCheckingResourceInterface;
+    }
+
+    /**
+     * @param SelfCheckingResourceInterface $resource
+     */
+    public function isFresh(ResourceInterface $resource, int $timestamp): bool
+    {
+        $key = "$resource:$timestamp";
+
+        return self::$cache[$key] ??= $resource->isFresh($timestamp);
+    }
+}