Improve multimeter.html with modern web standards and better UX

- Added HTML5 semantic structure and accessibility improvements
- Updated Bootstrap to 5.3.3 and Chart.js to 4.4.6 with integrity hashes
- Improved responsive design with viewport meta tag
- Enhanced JavaScript code quality with proper error handling
- Added loading states and better user feedback
- Modernized chart implementation with better responsive behavior
- Fixed HTML validation issues and deprecated attributes
- Added collapsible developer information section
- Improved LCD display initialization with error handling

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: PBrunot