Update legal documents and localization for compliance and clarity

- Updated .env.example with legal operator details for compliance.
- Refactored Impressum, Privacy, and Terms pages to utilize a new LegalDocument component for improved structure and maintainability.
- Enhanced localization files to include legal content in both German and English, ensuring accurate representation of legal information.
- Improved i18n handling to support locale detection from Accept-Language headers.

landingpage/impressum.php

@@ -0,0 +1,9 @@
+<?php
+declare(strict_types=1);
+
+require __DIR__ . '/includes/bootstrap.php';
+require __DIR__ . '/includes/layout.php';
+
+$locale = detect_locale();
+$messages = load_messages($locale);
+render_legal_page($config, $messages, $locale, 'impressum');