Bump flask from 3.1.0 to 3.1.1 in /src (#4107)

Bumps [flask](https://github.com/pallets/flask) from 3.1.0 to 3.1.1.
- [Release notes](https://github.com/pallets/flask/releases)
- [Changelog](https://github.com/pallets/flask/blob/main/CHANGES.rst)
- [Commits](pallets/flask@3.1.0...3.1.1)

---
updated-dependencies:
- dependency-name: flask
  dependency-version: 3.1.1
  dependency-type: direct:production
...

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Author: dependabot[bot]

src/requirements.txt

@@ -1,4 +1,4 @@
-flask==3.1.0
+flask==3.1.1
 flask-talisman==1.1.0
 gunicorn==23.0.0
 pytest==8.3.5