Bump gunicorn from 22.0.0 to 23.0.0 in /backend

Bumps [gunicorn](https://github.com/benoitc/gunicorn) from 22.0.0 to 23.0.0.
- [Release notes](https://github.com/benoitc/gunicorn/releases)
- [Commits](benoitc/gunicorn@22.0.0...23.0.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

backend/requirements.txt

@@ -3,7 +3,7 @@ flask-cors==4.0.2
 requests==2.32.3
 beautifulsoup4==4.12.2
 openai
-gunicorn==22.0.0
+gunicorn==23.0.0
 python-dotenv==1.0.0
 openai-agents
 firecrawl-py