test: remove unnecessary fixture dependency

[matthewelwell]

Changes

Removes the unnecessary dependency on the environment fixture in the feature fixture.

There were a few issues that arose from this that needed fixing - some were legitimate bugs that were picked up by this change, but others were just poorly written tests. Note that in resolving some of the resulting issues in the github integration logic, I also resolved a few typing issues that I noticed.

How did you test this code?

Ran the test suite.

[vercel]

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3 Skipped Deployments

Name	Status	Preview	Comments	Updated (UTC)
docs	⬜️ Ignored (Inspect)	Visit Preview		Jul 8, 2025 0:08am
flagsmith-frontend-preview	⬜️ Ignored (Inspect)	Visit Preview		Jul 8, 2025 0:08am
flagsmith-frontend-staging	⬜️ Ignored (Inspect)			Jul 8, 2025 0:08am

[github-actions]

Docker builds report

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-e2e:pr-5723	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-api-test:pr-5723	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-frontend:pr-5723	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-api:pr-5723	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith:pr-5723	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-private-cloud:pr-5723	Finished ✅	Results ✅

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.77%. Comparing base (a6a5b06) to head (9698e88).
Report is 3 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@## main #5723 +/- ##
=======================================
Coverage 97.77% 97.77% =======================================
Files 1255 1255 Lines 44317 44317 =======================================
Hits 43331 43331 Misses 986 986 

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[khvn26]

All changes LGTM, with one extremely minor comment.