Issue #3610362: Show seconds in admin trace timestamps via a dedicated, overridable date format

Closes #3610362.

The process-instance trace Arrived/Updated columns and the workflow-version list Created column used the named short date format (minute precision), so steps within the same minute were indistinguishable.

This ships an unlocked orchestra_datetime date format (default Y-m-d H:i:s) in orchestra_ui/config/install and uses it in OrchestraUiController (trace) and WorkflowVersionController (version list). Because it is a named, unlocked format, admins can change the pattern at Config » Regional » Date and time formats and multilingual sites can localize it, so no one is locked into the ISO default.

Customer-facing token timestamps keep the friendlier medium format. No update hook: Orchestra is pre-release, so the format installs with the module.