Bump flask-cors from 5.0.1 to 6.0.0 in /backend

Bumps [flask-cors](https://github.com/corydolphin/flask-cors) from 5.0.1 to 6.0.0.
- [Release notes](https://github.com/corydolphin/flask-cors/releases)
- [Changelog](https://github.com/corydolphin/flask-cors/blob/main/CHANGELOG.md)
- [Commits](corydolphin/flask-cors@5.0.1...6.0.0)

---
updated-dependencies:
- dependency-name: flask-cors
  dependency-version: 6.0.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

backend/requirements.txt

@@ -5,7 +5,7 @@ charset-normalizer==3.4.2
 click==8.1.8
 cryptography==44.0.1
 Flask==3.1.0
-flask-cors==5.0.1
+flask-cors==6.0.0
 Flask-JWT-Extended==4.7.1
 idna==3.10
 itsdangerous==2.2.0