Migrate Model.query to db.session.execute(select(...)) for SQLAlchemy 2.x compatibility

[catinhere]

As part of the Flask 3 / SQLAlchemy 2.x upgrade (#1098), Model.query is deprecated in Flask-SQLAlchemy 3.x and will be removed in a future version. Query.get() is also deprecated in SA 2.x in favour of db.session.get(). Both currently still work but emit deprecation warnings.

Scope

~62 production call sites across:

• compair/api/ — answer.py, assignment.py, classlist.py, comparison.py, gradebook.py, impersonation.py, lti_launch.py, lti_course.py, login.py, report.py, users.py
• compair/models/ — comparison.py, assignment_grade.py, answer_score.py, and others
• compair/manage/

~85 test-side usages in compair/tests/api/

Migration pattern

Before

  answers = Answer.query.filter_by(assignment_id=assignment.id).all()

After

  answers = db.session.execute(
      select(Answer).where(Answer.assignment_id == assignment.id)
  ).scalars().all()

with_entities() calls also go away naturally in this sweep — columns move into the select() argument list.

Query.get() specifically

Before

  assignment = Assignment.query.get(assignment_id)

After

  assignment = db.session.get(Assignment, assignment_id)

References

• Flask-SQLAlchemy 3.x migration: https://flask-sqlalchemy.palletsprojects.com/en/3.1.x/changes/
• SA 2.0 migration guide: https://docs.sqlalchemy.org/en/20/changelog/migration_20.html