feat: add native code block feature with Prism highlighting and editor integration

- Implemented custom code block system for frontend and editors
- Integrated Prism.js for syntax highlighting (YAML + HTML support)
- Added copy-to-clipboard functionality with hover-based UI
- Introduced custom Gutenberg block for code input
- Added Classic Editor button for quick code insertion
- Implemented server-side rendering via the_content filter
- Added dedicated styling (code.css) with Dracula-inspired theme
- Added editor preview styling (editor.css) for visual consistency
- Ensured accessibility and keyboard support for copy button
- Optimized asset loading and versioning using filemtime()

This feature provides a lightweight, theme-native alternative to external code highlighting plugins.

style.css

@@ -5,7 +5,7 @@ Author: Zeitfresser
 Author URI: https://ztfr.eu/
 Theme URI: https://ztfr.eu/
 Description: Zeitfresser Wordpress Theme
-Version: 2.5
+Version: 2.6
 Tested up to: 6.2
 Requires PHP: 7.0
 License: GNU General Public License v2 or later