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

.gitignore

@@ -0,0 +1,41 @@
+# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
+
+# dependencies
+/node_modules
+/.pnp
+.pnp.*
+.yarn/*
+!.yarn/patches
+!.yarn/plugins
+!.yarn/releases
+!.yarn/versions
+
+# testing
+/coverage
+
+# next.js
+/.next/
+/out/
+
+# production
+/build
+
+# misc
+.DS_Store
+*.pem
+
+# debug
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+.pnpm-debug.log*
+
+# env files (can opt-in for committing if needed)
+.env*
+
+# vercel
+.vercel
+
+# typescript
+*.tsbuildinfo
+next-env.d.ts