Build(deps): Bump authlib from 1.6.7 to 1.6.9 in /backend in the uv group across 1 directory (#244)

Build(deps): Bump authlib in /backend in the uv group across 1 directory

Bumps the uv group with 1 update in the /backend directory: [authlib](https://github.com/authlib/authlib).


Updates `authlib` from 1.6.7 to 1.6.9
- [Release notes](https://github.com/authlib/authlib/releases)
- [Changelog](https://github.com/authlib/authlib/blob/main/docs/changelog.rst)
- [Commits](authlib/authlib@v1.6.7...v1.6.9)

---
updated-dependencies:
- dependency-name: authlib
  dependency-version: 1.6.9
  dependency-type: indirect
  dependency-group: uv
...

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Author: dependabot[bot]