feat: Next.js + Tailwind + shadcn/ui project skeleton

- create-next-app with TypeScript, App Router, Tailwind CSS
- shadcn/ui initialized with defaults (button component + utils)
- .env.example with DATABASE_URL and SESSION_SECRET placeholders
- README.md with docs/runbooks/ reference

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

postcss.config.mjs

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