Python 3.12 deprecates datetime.utcnow() with a DeprecationWarning and
it will be removed in a future release. Replace all call-site usages in
services, routes, and utils with datetime.now(UTC), and replace the
SQLAlchemy ORM column defaults (which used the bare function reference
datetime.utcnow) with lambda: datetime.now(UTC) so that the returned
objects are timezone-aware and consistent with Python best practice.
Affected: database/models.py, services/{stories,history,profiles,
channels,export_import}.py, routes/{profiles,tasks}.py, utils/tasks.py
