Allow narrators to re-record flagged recordings

[AevumDecessus]

Summary

• Narrators can now re-record a book directly from a flagged recording's detail page
• Previously flagged recordings are automatically deleted when a new recording is uploaded for the same book
• Flagged recordings no longer count toward a book's max_narrators limit

Test plan

• All 145 tests pass (docker compose run --rm test)
• Lint passes (ruff check .)
• CI and SonarCloud quality gate pass

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

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