Prune CSS utilities and add radial BG

Remove many unused CSS variables and utility classes from assets/css/output.css to slim down the generated stylesheet and simplify properties. Add bg-radial and a specific from color (rgba(95,26,186,0.35)) and adjust gradient/to classes. Update links/index.html to apply the new radial background, add a space-bg element, and comment out several decorative SVG/img elements used for visuals.

Author: codebythiago