Track .nvmrc in the repo (follow-up from #4876)

[frano-m]

Background

#4876 (Next.js 16 / findable-ui ^54 upgrade, merged via #4878) included a checklist item to add a .nvmrc pinned to 22.13.0, matching package.json engines.node and the CI Dockerfile (.gitlab/Dockerfile). The file was never committed because .nvmrc is explicitly gitignored (.gitignore:56).

Task

• Remove the .nvmrc entry from .gitignore
• Commit .nvmrc with 22.13.0

Acceptance

• .nvmrc is tracked on main and contains 22.13.0, in line with package.json engines.node and .gitlab/Dockerfile.