chore(01-01): bootstrap Next.js 16 with TypeScript, App Router, Tailwind CSS v4

- Created Next.js 16.2.6 project with App Router, src/ directory, TypeScript strict mode
- Configured Tailwind CSS v4 with postcss.config.mjs
- Simplified src/app/page.tsx to Welcome to ClientHub placeholder
- Updated layout.tsx with ClientHub metadata, Italian lang, viewport export (Next.js 16 API)
- Added .gitignore covering node_modules, .env*, .next/, build artifacts

Note: create-next-app installed Next.js 16.2.6 (latest stable) instead of 15.x — fully compatible upgrade

package.json

@@ -0,0 +1,26 @@
+{
+  "name": "clienthub",
+  "version": "0.1.0",
+  "private": true,
+  "scripts": {
+    "dev": "next dev",
+    "build": "next build",
+    "start": "next start",
+    "lint": "eslint"
+  },
+  "dependencies": {
+    "next": "16.2.6",
+    "react": "19.2.4",
+    "react-dom": "19.2.4"
+  },
+  "devDependencies": {
+    "@tailwindcss/postcss": "^4",
+    "@types/node": "^20",
+    "@types/react": "^19",
+    "@types/react-dom": "^19",
+    "eslint": "^9",
+    "eslint-config-next": "16.2.6",
+    "tailwindcss": "^4",
+    "typescript": "^5"
+  }
+}