Migrate all shadcn components into apps/web/components/ui/ so the web app
is fully independent from packages/ui for its UI layer. Update to the
latest shadcn base-nova style. Add missing semantic color variables
(success, warning, info, canvas), font-mono mapping, scrollbar styling,
and wrap Select items in SelectGroup for proper padding.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
