Issue #3594034: Format [event:deadline_formatted] in the owner's language
PdvEvent built deadline_formatted with format($deadline, 'medium') and no langcode, so the dormancy deadline rendered in the current (request or site) language - typically not the owner's at dispatch time. An owner's localized notification therefore showed an English date ("Sat, 13 Jun 2026"). A Set-language action in the model cannot fix it, since the token is formatted when the event data is built.
Now formats with the owner's preferred langcode, matching pdv_mail and pdv_message. Kernel-test regression guard included (verified failing without the fix).