BlueBoxed v1.4.0

Major Upgrades:
- Modern Glassmorphism UI
- Dark Mode Support
- Accessible dark-mode toggle with system preference fallback and remembered user choice
- Accessibility Enhancements
- theme.json Added
- Security Improvements
- Performance Optimizations
- Better Focus States
- Modern CSS Variables
- Sticky Header Improvements

Prepared for WordPress.org enhancement workflow.
