Update uvicorn requirement from ~=0.41.0 to ~=0.42.0 in /backend

Updates the requirements on [uvicorn](https://github.com/Kludex/uvicorn) to permit the latest version.
- [Release notes](https://github.com/Kludex/uvicorn/releases)
- [Changelog](https://github.com/Kludex/uvicorn/blob/main/docs/release-notes.md)
- [Commits](Kludex/uvicorn@0.41.0...0.42.0)

---
updated-dependencies:
- dependency-name: uvicorn
  dependency-version: 0.42.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

backend/requirements.txt

@@ -1,3 +1,3 @@
 fastapi~=0.135.1
 pillow~=12.1.1
-uvicorn~=0.41.0
+uvicorn~=0.42.0