build(deps): bump python-multipart in /src/backend-api

Bumps [python-multipart](https://github.com/Kludex/python-multipart) from 0.0.22 to 0.0.26.
- [Release notes](https://github.com/Kludex/python-multipart/releases)
- [Changelog](https://github.com/Kludex/python-multipart/blob/main/CHANGELOG.md)
- [Commits](Kludex/python-multipart@0.0.22...0.0.26)

---
updated-dependencies:
- dependency-name: python-multipart
  dependency-version: 0.0.26
  dependency-type: direct:production
...

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

Author: dependabot[bot]

src/backend-api/pyproject.toml

@@ -17,7 +17,7 @@ dependencies = [
     "httpx==0.28.1",
     "pydantic-settings==2.10.1",
     "python-dotenv",
-    "python-multipart==0.0.22",
+    "python-multipart==0.0.26",
     "protobuf==7.34.0",
     "sas-cosmosdb==0.1.4",
     "semantic-kernel[azure]==1.40.0",