v1.0.4

Version 1.0.4 release

Update version number and add comprehensive release notes:

- Updated plugin version from 1.0.3 to 1.0.4
- Added detailed changelog documenting all 19 new features
- Documented 5 critical security fixes
- Added upgrade notes with step-by-step guidance
- Updated version history summary

This release includes:
- Complete UI redesign with modern interface
- Dashboard and logs viewer pages
- Backup codes system
- Role mapping and email restrictions
- Import/export functionality
- 5 critical security patches
- Performance optimizations
- Improved accessibility

Files Modified:
- cloudflare-zero-trust-login.php: Version 1.0.3 -> 1.0.4
- CHANGELOG.md: Complete 1.0.4 release notes