Bump anyio from 4.6.2.post1 to 4.9.0

Bumps [anyio](https://github.com/agronholm/anyio) from 4.6.2.post1 to 4.9.0.
- [Release notes](https://github.com/agronholm/anyio/releases)
- [Changelog](https://github.com/agronholm/anyio/blob/master/docs/versionhistory.rst)
- [Commits](agronholm/anyio@4.6.2.post1...4.9.0)

---
updated-dependencies:
- dependency-name: anyio
  dependency-version: 4.9.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

src/backend/requirements.txt

@@ -8,7 +8,7 @@ aiosignal==1.3.1
     # via aiohttp
 annotated-types==0.7.0
     # via pydantic
-anyio==4.6.2.post1
+anyio==4.9.0
     # via
     #   httpx
     #   openai