Bump body-parser and express in /backend

Bumps [body-parser](https://github.com/expressjs/body-parser) and [express](https://github.com/expressjs/express). These dependencies needed to be updated together.

Updates `body-parser` from 1.20.3 to 2.2.1
- [Release notes](https://github.com/expressjs/body-parser/releases)
- [Changelog](https://github.com/expressjs/body-parser/blob/master/HISTORY.md)
- [Commits](expressjs/body-parser@1.20.3...v2.2.1)

Updates `express` from 4.21.2 to 5.1.0
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/master/History.md)
- [Commits](expressjs/express@4.21.2...v5.1.0)

---
updated-dependencies:
- dependency-name: body-parser
  dependency-version: 2.2.1
  dependency-type: direct:production
- dependency-name: express
  dependency-version: 5.1.0
  dependency-type: direct:production
...

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Author: dependabot[bot]