fix: honor log cleanup cancellation

[vycdev2]

Summary

• pass the Quartz cancellation token to the old-log bulk deletion
• add a regression test proving pre-canceled cleanup preserves expired logs

Verification

• dotnet test Morpheus.Tests/Morpheus.Tests.csproj --no-restore --filter FullyQualifiedName~DeleteOldLogsJobTests — passed: 1 test
• dotnet build — passed: 0 errors (existing SQLite package advisory warning)
• dotnet test --no-build — passed: 429, skipped: 1
• git diff --check — passed

Risk

• Low: the behavior changes only when Quartz requests cancellation; normal cleanup retains the existing query and logging.

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.