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/filesystem/Exception/FileNotFoundException.php

@@ -0,0 +1,34 @@
+<?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\Filesystem\Exception;
+
+/**
+ * Exception class thrown when a file couldn't be found.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ * @author Christian Gärtner <christiangaertner.film@googlemail.com>
+ */
+class FileNotFoundException extends IOException
+{
+    public function __construct(?string $message = null, int $code = 0, ?\Throwable $previous = null, ?string $path = null)
+    {
+        if (null === $message) {
+            if (null === $path) {
+                $message = 'File could not be found.';
+            } else {
+                $message = \sprintf('File "%s" could not be found.', $path);
+            }
+        }
+
+        parent::__construct($message, $code, $previous, $path);
+    }
+}