build(deps): update python-dotenv requirement in /server/ai-gateway

Updates the requirements on [python-dotenv](https://github.com/theskumar/python-dotenv) to permit the latest version.
- [Release notes](https://github.com/theskumar/python-dotenv/releases)
- [Changelog](https://github.com/theskumar/python-dotenv/blob/main/CHANGELOG.md)
- [Commits](theskumar/python-dotenv@v1.0.0...v1.2.2)

---
updated-dependencies:
- dependency-name: python-dotenv
  dependency-version: 1.2.2
  dependency-type: direct:production
...

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

Author: dependabot[bot]

server/ai-gateway/requirements.txt

@@ -6,7 +6,7 @@ pydantic>=2.0.0
 redis>=5.0.0
 python-jose[cryptography]>=3.3.0
 httpx>=0.27.0
-python-dotenv>=1.0.0
+python-dotenv>=1.2.2
 python-json-logger>=2.0.0,<4.0.0
 google-genai>=1.0.0
 python-multipart>=0.0.7