Bump starlette from 0.47.2 to 0.49.1 in /src/backend

Bumps [starlette](https://github.com/Kludex/starlette) from 0.47.2 to 0.49.1.
- [Release notes](https://github.com/Kludex/starlette/releases)
- [Changelog](https://github.com/Kludex/starlette/blob/main/docs/release-notes.md)
- [Commits](Kludex/starlette@0.47.2...0.49.1)

---
updated-dependencies:
- dependency-name: starlette
  dependency-version: 0.49.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

src/backend/requirements.txt

@@ -306,7 +306,7 @@ sqlalchemy==2.0.41
     # via fastapi-app (pyproject.toml)
 sse-starlette==2.4.1
     # via mcp
-starlette==0.47.2
+starlette==0.49.1
     # via
     #   fastapi
     #   mcp