refactor: scaffold shadcn/ui on the existing Tailwind v3 setup

Adds components.json, cn() util, Radix + cva/clsx/tailwind-merge/
lucide-react/sonner deps, and CSS-variable color tokens mapped onto
the brand's existing pink-500 primary (#ec4899) and neutral grays.

`shadcn init` defaulted to Tailwind v4-style output (oklch colors,
`@theme`-driven CSS, `tw-animate-css`) without updating
tailwind.config.ts, which would not have compiled against the
project's pinned Tailwind v3. Hand-wrote the classic v3 integration
instead (HSL vars + tailwind.config.ts color/radius mapping +
tailwindcss-animate) rather than pull in an unplanned Tailwind
major-version migration.

Also drops the sunset/neon/pastel raw color scales from
tailwind.config.ts: grep confirmed no class ever referenced them,
they were leftover from before lib/themes.ts.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

package.json

@@ -16,12 +16,18 @@
   "dependencies": {
     "@prisma/client": "^5.15.0",
     "canvas-confetti": "^1.9.3",
+    "class-variance-authority": "^0.7.1",
+    "clsx": "^2.1.1",
     "framer-motion": "^11.3.0",
+    "lucide-react": "^1.27.0",
     "nanoid": "^5.0.7",
     "next": "14.2.35",
     "qrcode": "^1.5.4",
+    "radix-ui": "^1.6.7",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
+    "sonner": "^1.5.0",
+    "tailwind-merge": "^3.6.0",
     "zod": "^3.23.8"
   },
   "devDependencies": {
@@ -36,6 +42,7 @@
     "postcss": "^8.4.39",
     "prisma": "^5.15.0",
     "tailwindcss": "^3.4.6",
+    "tailwindcss-animate": "^1.0.7",
     "tsx": "^4.16.0",
     "typescript": "^5.5.3"
   }