build(deps): bump @sentry/nextjs from 7.113.0 to 8.15.0 in /backend

Bumps [@sentry/nextjs](https://github.com/getsentry/sentry-javascript) from 7.113.0 to 8.15.0.
- [Release notes](https://github.com/getsentry/sentry-javascript/releases)
- [Changelog](https://github.com/getsentry/sentry-javascript/blob/develop/CHANGELOG.md)
- [Commits](getsentry/sentry-javascript@7.113.0...8.15.0)

---
updated-dependencies:
- dependency-name: "@sentry/nextjs"
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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