Remove ~140 Tailwind utility classes from product.ex and cart.ex, replacing
with semantic CSS classes in components.css. Delete helper functions that
generated Tailwind class strings (card_classes, image_container_classes,
content_padding_class, title_classes, hero_cta_classes, grid_classes).
Use data-* attributes for variant styling, grid columns, and sticky
positioning. Update theme-layer2 selectors for renamed classes.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>