chore(deps): bump idna from 3.6 to 3.7 in /backend

Bumps [idna](https://github.com/kjd/idna) from 3.6 to 3.7.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.rst)
- [Commits](kjd/idna@v3.6...v3.7)

---
updated-dependencies:
- dependency-name: idna
  dependency-type: direct:production
...

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

backend/requirements.txt

@@ -45,7 +45,7 @@ httpcore==1.0.5
     # via httpx
 httpx==0.27.0
 icalendar==5.0.12
-idna==3.6
+idna==3.7
     # via
     #   anyio
     #   email-validator