- completely redesign hash generator UI with modern responsive layout

- add dark mode support with CSS variables
- improve file hashing functionality with drag-and-drop support
- implement real-time hash generation with debouncing
- add copy/clear functionality with visual feedback
- display algorithm info for educational purposes
- streamline algorithm options and organize into radio buttons
- add status indicators for better user feedback
- optimize for mobile viewing with responsive design

Author: TobiasMue91