chore(deps): update dependency flask to v3.1.2

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
flask (changelog)	==3.1.0 → ==3.1.2

---

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

---

Configuration

📅 Schedule: Branch creation - Between 10:00 AM and 10:59 AM, only on Saturday ( * 10 * * SAT ) in timezone America/Chicago, Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

---

• If you want to rebase/retry this PR, check this box

---

This PR was generated by Mend Renovate. View the repository job log.