chore(deps): bump uvicorn from 0.47.0 to 0.48.0 in /backend

Bumps [uvicorn](https://github.com/Kludex/uvicorn) from 0.47.0 to 0.48.0.
- [Release notes](https://github.com/Kludex/uvicorn/releases)
- [Changelog](https://github.com/Kludex/uvicorn/blob/main/docs/release-notes.md)
- [Commits](https://github.com/Kludex/uvicorn/compare/0.47.0...0.48.0)

---
updated-dependencies:
- dependency-name: uvicorn
  dependency-version: 0.48.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

backend/requirements.txt

@@ -1,6 +1,6 @@
 # Core Framework
 fastapi==0.136.3  # Updated: Fixed starlette DoS vulnerabilities (was 0.109.1); pulls in starlette>=1.0.0
-uvicorn[standard]==0.47.0
+uvicorn[standard]==0.48.0
 pydantic==2.13.4
 pydantic-settings==2.14.1