Add Next.js + shadcn/ui scaffold with deps

- Next.js 15 App Router, TypeScript, Tailwind CSS
- shadcn/ui components: button, input, select, textarea, dialog, tabs, table, card, badge, label, separator, dropdown-menu, form, sheet, tooltip
- Runtime deps: @tanstack/react-table, zod, react-hook-form, @hookform/resolvers, lucide-react, date-fns

web/postcss.config.mjs

@@ -0,0 +1,7 @@
+const config = {
+  plugins: {
+    "@tailwindcss/postcss": {},
+  },
+};
+
+export default config;