chore(deps)(deps): bump python-multipart in /backend

Bumps [python-multipart](https://github.com/Kludex/python-multipart) from 0.0.20 to 0.0.22.
- [Release notes](https://github.com/Kludex/python-multipart/releases)
- [Changelog](https://github.com/Kludex/python-multipart/blob/master/CHANGELOG.md)
- [Commits](Kludex/python-multipart@0.0.20...0.0.22)

---
updated-dependencies:
- dependency-name: python-multipart
  dependency-version: 0.0.22
  dependency-type: direct:production
...

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

Author: dependabot[bot]

backend/requirements.txt

@@ -21,7 +21,7 @@ redis[hiredis]==5.0.1
 # Authentication & Security
 python-jose[cryptography]==3.5.0  # Security: Fixed algorithm confusion and JWT bomb (PYSEC-2024-232, PYSEC-2024-233)
 bcrypt==5.0.0
-python-multipart==0.0.20  # Security: Fixed ReDoS vulnerabilities (GHSA-2jv5-9r88-3w3p, GHSA-59g5-xgcq-4qw3)
+python-multipart==0.0.22  # Security: Fixed ReDoS vulnerabilities (GHSA-2jv5-9r88-3w3p, GHSA-59g5-xgcq-4qw3)
 pydantic[email]==2.12.5
 pydantic-settings==2.12.0  # Upgraded: Compatible with pydantic 2.11.7