fix: skip-audit-log-for-soft-deleted-CR

[Zaimwa9]

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Closes #6248

Context

Edge-case that is a combination between data corruption when migrating to feature versioning and trying to delete a project.
When migrating, feature states from committed CR where linked to EFV with:

• A change_request_id
• live_from = None
  When deleting the project, the soft-delete was triggering the hook here without live_from which raised the NoneType error

Changes

• Updated hook AFTER_SAVE to ignore CR with deleted_at

How did you test this code?

• Added a test (fails without change)
• Manually

1. Create a new project (feature_versioning_v2 disabled)
2. Create and publish a change request now (it must have existing CR)
3. Create a change request in the future
4. Publish it
5. Enable feature_versioning_v2
6. Delete the project

[vercel]

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3 Skipped Deployments

Project	Deployment	Preview	Comments	Updated (UTC)
docs	Ignored	Preview		Dec 4, 2025 5:19pm
flagsmith-frontend-preview	Ignored	Preview		Dec 4, 2025 5:19pm
flagsmith-frontend-staging	Ignored	Preview		Dec 4, 2025 5:19pm

[github-actions]

Docker builds report

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-e2e:pr-6367	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-frontend:pr-6367	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-api:pr-6367	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith:pr-6367	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-private-cloud:pr-6367	Finished ✅	Results ✅

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.02%. Comparing base (ab32904) to head (05ef502).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6367   +/-   ##
=======================================
  Coverage   98.02%   98.02%           
=======================================
  Files        1282     1282           
  Lines       45498    45513   +15     
=======================================
+ Hits        44600    44615   +15     
  Misses        898      898           

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[Zaimwa9]

I believe this is the less risky place to fix this issue.

I preferred not to add a guard against live_from = None because for any similar bug it would have entered the wrong branch and create an irrelevant log create_feature_state_updated_by_change_request_audit_log