Move the 3 theme layer imports (primitives, layer2-attributes, semantic)
out of admin.css and shop.css into a new theme.css bundle loaded by all
root layouts. Eliminates 28 KB of duplication on admin pages where both
admin.css and shop.css were each embedding the same theme CSS.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Phase 7: add LoadTheme to base :browser pipeline so auth and setup
pages get theme settings. Update root.html.heex with .themed wrapper,
font preloads, layer declaration, and generated CSS injection.
Remove old data-theme JS toggle script.
Phase 8: upgrade admin/reset.css to a proper @layer reset matching
the shop reset structure. Remove dead theme toggle CSS rules.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
