Update sqlalchemy version to 2.x

[ahsentekd]

Hello, the sqlalchemy version is outdated so i need to keep update.

[nobodynate]

Thank you for this PR! After reviewing the codebase, here's what needs to be done for a complete SQLAlchemy 2.0 upgrade:

Required changes:

1. Update pyproject.toml - Change SQLAlchemy = "~1.3.0" to SQLAlchemy = "^2.0.0"

2. Run poetry lock - Regenerate the lock file (don't manually edit requirements.txt)

3. Migrate legacy query() API - SQLAlchemy 2.0 deprecates the query API. Need to update 14 occurrences:

   • session.query(Model).filter(...).all() → session.scalars(select(Model).where(...)).all()
   • session.query(Model).scalar() → session.scalars(select(Model)).first()
   • Add select import: from sqlalchemy import select

4. Rebase onto current master - Resolve conflicts with recently merged PRs

Files to update:

• pyproject.toml (SQLAlchemy version)
• pacu/main.py (9 query calls + add select import)
• pacu/core/models.py (3 query calls + add select import)
• tests/test_pacu_session.py (1 query call)
• conftest.py (1 query call)

The codebase doesn't use other deprecated features (autocommit, engine.execute), so the migration is straightforward. Let us know if you'd like help with the migration!