- complete redesign of csv/json converter with dark mode support

- add tabs for csv-to-json and json-to-csv conversion directions
- implement drag-and-drop file upload functionality
- add direct text input option with sample data examples
- improve conversion options (pretty/minify json, header handling)
- enhance UI with responsive design and better visual feedback
- add copy to clipboard functionality
- improve file handling with auto-populated output filenames
- replace sidebar.js with logo.js reference

Author: TobiasMue91