Bump openai from 1.66.2 to 1.66.3 in /backend

Bumps [openai](https://github.com/openai/openai-python) from 1.66.2 to 1.66.3.
- [Release notes](https://github.com/openai/openai-python/releases)
- [Changelog](https://github.com/openai/openai-python/blob/main/CHANGELOG.md)
- [Commits](openai/openai-python@v1.66.2...v1.66.3)

---
updated-dependencies:
- dependency-name: openai
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

backend/poetry.lock

@@ -35,7 +35,7 @@ gunicorn = "^23.0.0"
 humanize = "^4.11.0"
 lxml = "^5.3.0"
 markdown = "^3.7"
-openai = "^1.60.1"
+openai = "^1.66.3"
 psycopg = "^3.2.4"
 pygithub = "^2.5.0"
 python = "^3.13"