fix: honor activity role job cancellation

[vycdev2]

Summary

• honor Quartz cancellation before loading activity-role guilds and while pacing role reconciliation
• propagate cancellation through EF persistence instead of logging and continuing during host shutdown
• add a regression test proving a pre-canceled execution exits with cancellation

Verification

• dotnet build --no-restore --verbosity minimal — passed (0 errors; existing NU1903 SQLite package warning)
• dotnet test Morpheus.Tests/Morpheus.Tests.csproj --no-build --filter FullyQualifiedName~ActivityRolesJobTests --logger 'console;verbosity=minimal' — passed (1/1)
• dotnet test Morpheus.Tests/Morpheus.Tests.csproj --no-build --logger 'console;verbosity=minimal' — passed (429 passed, 1 skipped)
• git diff --check upstream/develop...HEAD — passed
• regression proof: the new test failed against untouched develop because no cancellation was propagated, then passed with this change

Risk

• Low: the change affects only shutdown/interruption behavior; normal activity-role assignment logic is unchanged.

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