security: OWASP audit and hardening (v1.0.8)

- Archive XSS: wrap get_the_archive_title/description with wp_kses_post()
  in ContextBuilder to sanitize Editor-editable term content rendered via |raw
- Comment fields: esc_html() on comment_author, esc_url() on comment_author_url
  at data source; template updated to output pre-escaped URL via |raw
- dark-mode.js: whitelist localStorage value against ['dark','light'] to
  prevent attribute injection from third-party script tampering
- TwigService: add is_safe=>html to esc_html/esc_attr/esc_url Twig functions
  to prevent double-encoding if autoescape is ever enabled
- Add .markdownlint.json (disable MD024 duplicate headings, MD013 line length)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

style.css

@@ -7,7 +7,7 @@ Description: A modern WordPress Block Theme built from scratch with Bootstrap 5.
 Requires at least: 6.7
 Tested up to: 6.7
 Requires PHP: 8.3
-Version: 1.0.7
+Version: 1.0.8
 License: GNU General Public License v2 or later
 License URI: http://www.gnu.org/licenses/gpl-2.0.html
 Text Domain: wp-bootstrap