refactor: migrer datetime.utcnow() vers datetime.now(UTC)

Co-authored-by: OpenAI/GPT-5.6-terra <vibecoder@antoineve.me>

app/models.py

@@ -1,4 +1,4 @@
-from datetime import date, datetime, time
+from datetime import UTC, date, datetime, time
 
 import sqlalchemy as sa
 import sqlalchemy.orm as so
@@ -27,9 +27,11 @@ class WorkEntry(db.Model):
     motor_vehicle_id: so.Mapped[str | None] = so.mapped_column(sa.String(64), nullable=True)
     day_type: so.Mapped[str] = so.mapped_column(sa.String(16), nullable=False, default="WORK")
     comment: so.Mapped[str | None] = so.mapped_column(sa.Text, nullable=True)
-    created_at: so.Mapped[datetime] = so.mapped_column(sa.DateTime, default=datetime.utcnow)
+    created_at: so.Mapped[datetime] = so.mapped_column(
+        sa.DateTime, default=lambda: datetime.now(UTC)
+    )
     updated_at: so.Mapped[datetime] = so.mapped_column(
-        sa.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow
+        sa.DateTime, default=lambda: datetime.now(UTC), onupdate=lambda: datetime.now(UTC)
     )
 
     time_slots: so.Mapped[list["TimeSlot"]] = so.relationship(