fix(Webhooks): Correct previous_state for scheduled feature updates

[emyller]

Webhook consumers receive the correct previous state when a scheduled feature update goes live.

Changes

• Webhook previous_state reflects the actual previous live feature state for scheduled changes
• Integration tests cover scheduled flag change webhooks in legacy versioning

Closes #2063

Review effort: 2/5

[vercel]

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3 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
docs	Ignored	Preview	Feb 20, 2026 0:35am
flagsmith-frontend-preview	Ignored	Preview	Feb 20, 2026 0:35am
flagsmith-frontend-staging	Ignored	Preview	Feb 20, 2026 0:35am

[github-actions]

Docker builds report

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-e2e:pr-6740	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-api-test:pr-6740	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-frontend:pr-6740	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-api:pr-6740	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-private-cloud:pr-6740	Finished ✅	Results ✅

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.25%. Comparing base (7c0bf27) to head (dfe89e0).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6740      +/-   ##
==========================================
+ Coverage   98.23%   98.25%   +0.02%     
==========================================
  Files        1312     1312              
  Lines       48490    48547      +57     
==========================================
+ Hits        47633    47701      +68     
+ Misses        857      846      -11     

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