db.py:
- Add conn.isolation_level = None to get_conn() — fixes row_factory +
autocommit conflict. row_factory disables implicit transactions,
so we need explicit autocommit mode.
- Remove all conn.commit() calls (unnecessary with autocommit)
pyproject.toml:
- Move pytest + pytest-asyncio to main dependencies (uv run pytest
uses ephemeral env with main deps only)
tests/test_db.py:
- Fix test_upsert_user_updates_username to not chain upsert_user()
calls in assert expressions (test isolation issue)
