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
list_stories() previously executed one COUNT(story_items) query per
story in a Python loop. With N stories that is N+1 round-trips to
SQLite regardless of list length. Replace with a single aggregated
GROUP BY query that fetches all counts at once, then populate each
StoryResponse from a dict lookup.
