Add premium-web-design skill

Adds a new skill under creative-design for generating premium,
Awwwards-quality website designs as React components. Teaches Claude
the AI-aesthetic blacklist, a 15-entry Structural DNA Catalog, deep
industry reference research, a Spline 3D playbook, and a 15-point
prompt checklist that every build must answer before writing JSX.

Author: sayginsaman