feat: add shadcn registry for source-code distribution

Add registry.json so devs can install the wheel picker's original
(pre-build) source via the shadcn CLI as an alternative to the npm package.

- add root registry.json (react-wheel-picker registry item)
- declare *.css module + switch package to bundler moduleResolution
- drop redundant ./dist/style.css export alias
- web: use ComponentProps import, switch ring -> inset-ring (Tailwind v4)
- bump turbo, use local turbo schema

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>