Update dependency flask to v3.1.3

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
flask (changelog)	3.1.1 → 3.1.3

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Release Notes

pallets/flask (flask)

v3.1.3

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This is the Flask 3.1.3 security fix release, which fixes a security issue but does not otherwise change behavior and should not result in breaking changes compared to the latest feature release.

PyPI: https://pypi.org/project/Flask/3.1.3/
Changes: https://flask.palletsprojects.com/page/changes/#version-3-1-3

• The session is marked as accessed for operations that only access the keys but not the values, such as in and len. GHSA-68rp-wp8r-4726

v3.1.2

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Released 2025-08-19

• stream_with_context does not fail inside async views. :issue:5774
• When using follow_redirects in the test client, the final state
  of session is correct. :issue:5786
• Relax type hint for passing bytes IO to send_file. :issue:5776

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