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

eslint.config.mjs

@@ -0,0 +1,18 @@
+import { defineConfig, globalIgnores } from "eslint/config";
+import nextVitals from "eslint-config-next/core-web-vitals";
+import nextTs from "eslint-config-next/typescript";
+
+const eslintConfig = defineConfig([
+  ...nextVitals,
+  ...nextTs,
+  // Override default ignores of eslint-config-next.
+  globalIgnores([
+    // Default ignores of eslint-config-next:
+    ".next/**",
+    "out/**",
+    "build/**",
+    "next-env.d.ts",
+  ]),
+]);
+
+export default eslintConfig;