Update nextjs-contentful-store project setup

[pfferrari]

Closes commercelayer/issues-app/issues/710

What I did

Updated packages

Package	From	To
next	13.1.6	16.3.4
react / react-dom	18.2.0	19.2.8
@commercelayer/react-components	4.2.2	5.0.1
contentful	9.3.3	11.12.10
tailwindcss	3.4.7	4.3.3
@headlessui/react	1.5.0	2.2.10
eslint	8.34	9.39.1
typescript	4.5.5	5.9.3
prettier	2.5.1	3.9.6

ESLint stays on 9 (eslint-config-next@16 pulls typescript-eslint@^8); TypeScript on 5.9 by choice.

Migrations

• Contentful — Entry<Fields> no longer exists; typings rewritten as 7 EntrySkeletonTypes, images retyped as Asset, withoutUnresolvableLinks modifier. Also fixed getProduct, which queried a non-existent key.
• CL v5 — <CommerceLayer> dropped endpoint, <OrderContainer> → <Order>, subpath exports removed.
• Cart — iframe-resizer v5 is GPL-3.0, so the dependency was removed rather than upgraded: the custom iframe is now CL's <HostedCart />, plus a container min-height and an SSR token guard it requires.
• Tailwind 4 — CSS-first config; caught 2 silent visual regressions (shadow-sm remapped, colourless border-2).
• ESLint / React 19 — flat config, formatting left to Prettier; 2 setState-in-effect violations fixed by deriving state.
• Pages Router kept deliberately; App Router migration not done.

Security

• pnpm audit: 14 → 1, all 14 dev-only (pnpm audit --prod clean).
• Fixed with same-major transitive overrides in pnpm-workspace.yaml.
• uuid@9 left knowingly: the advisory needs a buf argument, the only call site is v4() with none.

Cleanup & fixes

• Removed 12 unused deps; added lodash, imported in 8 files but never declared.
• Removed NEXT_PUBLIC_CL_ENDPOINT — unused after v5. Changes the deploy button URLs.
• Fixed a pre-existing bug: unknown country codes returned 500 instead of 404.

Verification

• typecheck, lint, build clean. All routes exercised against a live Contentful space — 200s with zero runtime errors, /xx/en-us → 404.
• Known non-issue: /fr/fr-fr returns 500 because the space has only it-IT and en-US enabled.

Checklist (general changes)

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests).
• Make sure to add/update documentation regarding your changes.
• You are NOT deprecating/removing a feature.