ci: Add known SDK version workflow

[khvn26]

Contributes to #5861.

Thanks for submitting a PR! Please check the boxes below:

• I have added information to docs/ if required so people know about the feature!
• I have filled in the "Changes" section below?
• I have filled in the "How did you test this code" section below?
• I have used a Conventional Commit title for this Pull Request

Changes

This PR adds a dispatchable workflow to automatically open PRs with SDK allow list updates.
The workflow makes sure that the currently present versions are persisted in the same order, and appends a new version to the list.

How did you test this code?

Tested the Makefile target locally. Will test end-to-end once the PR is merged.

[vercel]

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3 Skipped Deployments

Project	Deployment	Preview	Comments	Updated (UTC)
docs	Ignored	Preview		Sep 9, 2025 2:10pm
flagsmith-frontend-preview	Ignored	Preview		Sep 9, 2025 2:10pm
flagsmith-frontend-staging	Ignored	Preview		Sep 9, 2025 2:10pm

[github-actions]

Docker builds report

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-private-cloud:pr-6032	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-e2e:pr-6032	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-frontend:pr-6032	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-api-test:pr-6032	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-api:pr-6032	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith:pr-6032	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-private-cloud:pr-6032	Finished ✅	Results ✅

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.99%. Comparing base (4f67003) to head (0e7fa03).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6032   +/-   ##
=======================================
  Coverage   97.99%   97.99%           
=======================================
  Files        1275     1275           
  Lines       44892    44892           
=======================================
  Hits        43993    43993           
  Misses        899      899           

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[emyller]

Looks good but I think we'd be happier with less code?

[emyller]