build(deps-dev): bump typescript from 5.9.3 to 6.0.2 in /backend

Bumps [typescript](https://github.com/microsoft/TypeScript) from 5.9.3 to 6.0.2.
- [Release notes](https://github.com/microsoft/TypeScript/releases)
- [Commits](microsoft/TypeScript@v5.9.3...v6.0.2)

---
updated-dependencies:
- dependency-name: typescript
  dependency-version: 6.0.2
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]