Replace Bootstrap default dark grays and hardcoded colors with a
design-token system: surface levels, ink hierarchy, logo blue (#07addf)
as the single accent, mark-feed red for print indicators. Card browsers
get rounded corners, subtle borders, and hover-reveal action buttons.
- Default density to thick (2) for bolder output
- Default font size to 30pt for better readability
- Add draw.fontmode="1" to disable antialiasing for crisp 1-bit text
- Add ImageOps.autocontrast before thresholding images
- Update web GUI defaults to match CLI