Update dependency flask to v3.1.2

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
flask (changelog)	==3.1.0 → ==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

v3.1.1

Compare Source

Released 2025-05-13

• Fix signing key selection order when key rotation is enabled via
  SECRET_KEY_FALLBACKS. :ghsa:4grg-w6v8-c28g
• Fix type hint for cli_runner.invoke. :issue:5645
• flask --help loads the app and plugins first to make sure all commands
  are shown. :issue:5673
• Mark sans-io base class as being able to handle views that return
  AsyncIterable. This is not accurate for Flask, but makes typing easier
  for Quart. :pr:5659

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⚠️ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

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The artifact failure details are included below:

File name: uv.lock

Command failed: uv lock --upgrade-package flask
Using CPython 3.14.2 interpreter at: /opt/containerbase/tools/python/3.14.2/bin/python3
  × No solution found when resolving dependencies for split (markers:
  │ python_full_version == '3.12.*' and sys_platform == 'linux'):
  ╰─▶ Because there are no versions of huggingface-hub{sys_platform ==
      'linux'} and your project depends on huggingface-hub{sys_platform
      == 'linux'}, we can conclude that your project's requirements are
      unsatisfiable.

      hint: While the active Python version is 3.14, the resolution failed for
      other Python versions supported by your project. Consider limiting your
      project's supported Python versions using `requires-python`.