chore(deps): bump google-auth from 2.49.1 to 2.49.2 in /backend

Bumps [google-auth](https://github.com/googleapis/google-auth-library-python) from 2.49.1 to 2.49.2.
- [Release notes](https://github.com/googleapis/google-auth-library-python/releases)
- [Changelog](https://github.com/googleapis/google-auth-library-python/blob/main/CHANGELOG.md)
- [Commits](https://github.com/googleapis/google-auth-library-python/commits)

---
updated-dependencies:
- dependency-name: google-auth
  dependency-version: 2.49.2
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

backend/requirements.txt

@@ -29,7 +29,7 @@ email-validator==2.3.0
 
 # Gmail API (for direct email injection)
 google-api-python-client==2.193.0
-google-auth==2.49.1
+google-auth==2.49.2
 google-auth-oauthlib==1.3.1
 google-auth-httplib2==0.3.1