Adopt shadcn theme tokens and motion as the component styling foundation #58

Components hardcode zinc-* / emerald-* colours, so they ignore the consuming app's shadcn theme and look out of place next to the shadcn ecosystem (21st.dev, the shadcn registry).

Scope

• Style components with shadcn semantic tokens (bg-popover, text-muted-foreground, ring-ring/50, …).
• Add motion (animation) and lucide-react (icons) as runtime dependencies; externalise them in tsup.
• Define the tokens on the docs site; document them for npm consumers who don't use shadcn.
• Update the component conventions in ARCHITECTURE.md (tokens, classNames slots, motion + reduced motion).

Unblocks the per-component redesigns.