fix(FOUR-33645): guard activity execution time metric when ms timesta…

[gproly]

…mps are null

Prevent task completion failures when recording the Prometheus activity_execution_time_seconds histogram in BpmnSubscriber.

Fall back to created_at and completed_at when created_at_ms or completed_at_ms are unavailable, and skip the metric observation when either timestamp is still missing.

https://processmaker.atlassian.net/browse/FOUR-33645

ci:deploy

[cursor]

PR Summary

Low Risk
Observability-only change with defensive null handling on the activity-completed path; no auth, data, or workflow logic changes.

Overview
Hardens Prometheus activity duration recording in BpmnSubscriber::onActivityCompleted so task completion no longer fails when millisecond timestamps are absent.

Execution window now uses created_at_ms / completed_at_ms with fallback to created_at / completed_at. The activity_execution_time_seconds histogram is only observed when both start and end times are present; otherwise the metric is skipped and notifications/events proceed as before.

^{Reviewed by Cursor Bugbot for commit 499436d. Bugbot is set up for automated code reviews on this repo. Configure here.}

[decisions-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarQube

[vladyrichter]

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