feat(frontend): scaffold Vite+React+TS+Tailwind/ShadCn + Vitest

TDD: App-renders-ThothII test RED then GREEN. ShadCn v4 (base-nova style)
init + button/checkbox/radio-group/textarea/card/dialog/badge/sonner added.
tailwind.config.ts extended with oklch CSS-variable color mapping required
by ShadCn v4 @apply directives. npm test passes; npm run build clean.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/tsconfig.tsbuildinfo

@@ -0,0 +1 @@
+{"root":["./src/app.test.tsx","./src/app.tsx","./src/main.tsx","./src/components/ui/badge.tsx","./src/components/ui/button.tsx","./src/components/ui/card.tsx","./src/components/ui/checkbox.tsx","./src/components/ui/dialog.tsx","./src/components/ui/radio-group.tsx","./src/components/ui/sonner.tsx","./src/components/ui/textarea.tsx","./src/lib/utils.ts","./src/test/setup.ts"],"version":"5.9.3"}