Initial theme scaffolding (v0.0.1)

- Bootstrap 5 CSS/JS integration via Yarn (served locally)
- Dart Sass build pipeline with PostCSS, Autoprefixer, cssnano
- Twig 3.0 via Composer with PSR-4 autoloading
- FSE block theme templates (index, home, single, page, archive, search, 404)
- Template parts (header, footer) and block patterns
- theme.json with Bootstrap 5-aligned design tokens
- Gitea CI/CD workflow for automated release packages
- WordPress i18n support (en_US base, de_CH translation)

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

inc/Twig/TwigService.php

@@ -0,0 +1,72 @@
+<?php
+/**
+ * Twig Template Engine Service.
+ *
+ * @package WPBootstrap
+ * @since 0.0.1
+ */
+
+namespace WPBootstrap\Twig;
+
+use Twig\Environment;
+use Twig\Loader\FilesystemLoader;
+use Twig\TwigFunction;
+
+class TwigService
+{
+    private static ?TwigService $instance = null;
+    private Environment $twig;
+
+    private function __construct()
+    {
+        $viewsDir = get_template_directory() . '/views';
+        $cacheDir = WP_CONTENT_DIR . '/cache/twig';
+
+        $loader = new FilesystemLoader($viewsDir);
+        $this->twig = new Environment($loader, [
+            'cache' => WP_DEBUG ? false : $cacheDir,
+            'debug' => WP_DEBUG,
+            'auto_reload' => true,
+        ]);
+
+        $this->registerWordPressFunctions();
+    }
+
+    public static function getInstance(): self
+    {
+        if (self::$instance === null) {
+            self::$instance = new self();
+        }
+        return self::$instance;
+    }
+
+    public function render(string $template, array $context = []): string
+    {
+        return $this->twig->render($template, $context);
+    }
+
+    public function display(string $template, array $context = []): void
+    {
+        $this->twig->display($template, $context);
+    }
+
+    public function getEnvironment(): Environment
+    {
+        return $this->twig;
+    }
+
+    private function registerWordPressFunctions(): void
+    {
+        $this->twig->addFunction(new TwigFunction('__', function (string $text, string $domain = 'wp-bootstrap'): string {
+            return __($text, $domain);
+        }));
+
+        $this->twig->addFunction(new TwigFunction('_e', function (string $text, string $domain = 'wp-bootstrap'): void {
+            _e($text, $domain);
+        }));
+
+        $this->twig->addFunction(new TwigFunction('esc_html', 'esc_html'));
+        $this->twig->addFunction(new TwigFunction('esc_attr', 'esc_attr'));
+        $this->twig->addFunction(new TwigFunction('esc_url', 'esc_url'));
+    }
+}