Add Next.js 15 app skeleton with Tailwind v4 and shadcn/ui

Next.js 15 + React 19, Tailwind v4, shadcn/ui (button, card, input,
dialog), postcss config, standalone output. ESLint extended with
next/core-web-vitals via eslint-config-next flat export. node-linker=hoisted
in .npmrc to allow standalone builds on Windows (symlink restriction).
next-env.d.ts added to .gitignore.

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

.claude/settings.json

@@ -0,0 +1,12 @@
+{
+  "permissions": {
+    "allow": [
+      "Bash(pnpm add *)",
+      "Bash(pnpm dlx *)",
+      "Bash(pnpm install *)",
+      "Bash(pnpm build *)",
+      "Bash(pnpm lint *)",
+      "Bash(pnpm dev *)"
+    ]
+  }
+}