refactor: install shadcn/ui primitives (button, card, input, textarea, label, tabs, switch, dialog, alert-dialog, badge, separator, sonner)

Pinned the CLI to shadcn@2.3.0 rather than the latest (4.16.0): the
latest generation targets Tailwind v4-only syntax (bare-value parens
like `gap-(--card-spacing)`, the `in-*` variant, `--spacing()`) that
silently fails to compile under this project's Tailwind v3.4.6.
2.3.0 is the last CLI generation producing classic hsl(var(--x))
v3-compatible component output.

Swapped @radix-ui/react-icons for the already-installed lucide-react
in dialog.tsx, and dropped sonner's next-themes dependency (the app
has no dark-mode toggle, so Toaster is hardcoded to theme="light").

Old custom src/components/ui/Button.tsx, Card.tsx, and Field.tsx are
removed here; call sites are updated in the following commits.

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

package.json

@@ -15,6 +15,13 @@
   },
   "dependencies": {
     "@prisma/client": "^5.15.0",
+    "@radix-ui/react-alert-dialog": "^1.1.23",
+    "@radix-ui/react-dialog": "^1.1.23",
+    "@radix-ui/react-label": "^2.1.15",
+    "@radix-ui/react-separator": "^1.1.15",
+    "@radix-ui/react-slot": "^1.3.3",
+    "@radix-ui/react-switch": "^1.3.7",
+    "@radix-ui/react-tabs": "^1.1.21",
     "canvas-confetti": "^1.9.3",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
@@ -23,10 +30,9 @@
     "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",
+    "sonner": "^1.7.4",
     "tailwind-merge": "^3.6.0",
     "zod": "^3.23.8"
   },