PayloadDataDelete.deleteSubjectData('soft') was NULLing PII fields and
emitting RESTRICT audit entries, but never setting processingRestrictedAt
on self-kind rows — violating GDPR Art. 17 restriction semantics.
softRedactOwnerRows now accepts optional extraData; processOwnerRows
passes { processingRestrictedAt: new Date().toISOString() } when
kind === 'self' and mode === 'soft'. Owner-kind rows are intentionally
excluded (restriction flag belongs on the subject record, not owned rows).
Added two dedicated tests: one asserting the field is present for self,
one asserting it is absent for owner.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>