- completely redesigned UI with modern styling and dark mode support

- improved sketch conversion algorithm with multiple style options:
  - `outline`, `pencil`, `hatching`, and `charcoal`
- added advanced options for fine-tuning sketch parameters:
  - edge detection, texture, smoothing
- implemented post-processing filters (`aged`, `textured`)
- added image comparison slider view
- implemented drag-and-drop file upload
- added zoom controls for both original and sketch images
- moved processing to web worker for better performance
- added notifications system for user feedback
- improved accessibility with keyboard navigation support

Author: TobiasMue91