chore(deps): bump python-dotenv in /server/ai-gateway

Bumps [python-dotenv](https://github.com/theskumar/python-dotenv) from 1.2.2 to 1.2.3.
- [Release notes](https://github.com/theskumar/python-dotenv/releases)
- [Changelog](https://github.com/theskumar/python-dotenv/blob/main/CHANGELOG.md)
- [Commits](theskumar/python-dotenv@v1.2.2...v1.2.3)

---
updated-dependencies:
- dependency-name: python-dotenv
  dependency-version: 1.2.3
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

server/ai-gateway/requirements.txt

@@ -10,7 +10,7 @@ pydantic==2.13.4
 redis==8.0.1
 python-jose[cryptography]==3.5.0
 httpx==0.28.1
-python-dotenv==1.2.2
+python-dotenv==1.2.3
 python-json-logger==3.3.0
 google-genai>=1.0.0
 python-multipart==0.0.32