chore(deps): bump python-dotenv from 1.0.1 to 1.2.2 in /backend (#6)

Bumps [python-dotenv](https://github.com/theskumar/python-dotenv) from 1.0.1 to 1.2.2.
- [Release notes](https://github.com/theskumar/python-dotenv/releases)
- [Changelog](https://github.com/theskumar/python-dotenv/blob/main/CHANGELOG.md)
- [Commits](theskumar/python-dotenv@v1.0.1...v1.2.2)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

backend/requirements.txt

@@ -3,7 +3,7 @@ uvicorn[standard]==0.46.0
 pydantic==2.10.4
 pydantic-settings==2.7.1
 google-generativeai==0.8.4
-python-dotenv==1.0.1
+python-dotenv==1.2.2
 httpx==0.28.1
 redis[hiredis]==5.2.1
 asyncpg==0.31.0