Bump next from 15.1.4 to 15.5.6 in /realtime-csv-importer

Bumps [next](https://github.com/vercel/next.js) from 15.1.4 to 15.5.6.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v15.1.4...v15.5.6)

---
updated-dependencies:
- dependency-name: next
  dependency-version: 15.5.6
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]