Update dependency flask to v3.1.2

This MR contains the following updates:

Package	Type	Update	Change
flask (changelog)	ironbank-pypi	patch	3.1.1 -> 3.1.2

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Release Notes

pallets/flask (flask)

v3.1.2

Compare Source

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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