fix(sqlalchemy): update psycopg2 driver spec in connection urls

[CagriYonca]

Summary

Explicitly specify psycopg2 as the SQLAlchemy dialect driver in PostgreSQL
connection URLs and bump the psycopg2-binary lower bound to >=2.9.12.

Problem

1. SQLAlchemy 2.1 changed the default PostgreSQL driver to psycopg (v3)

With an unqualified postgresql:// URL, SQLAlchemy 2.1 now attempts to load
psycopg (v3) first. Since our test environment only installs psycopg2, this raises:

ModuleNotFoundError: No module named 'psycopg'

See: SQLAlchemy 2.1 Migration Guide

2. psycopg2-binary>=2.8.6 has no pre-built wheel for Python 3.12/3.13

On Python 3.12+, pip falls back to building from source, which fails due to
C-level incompatibilities introduced in those Python versions. Pre-built wheels
for Python 3.13 were introduced in psycopg2-binary 2.9.10. The >=2.9.12
lower bound guarantees a compatible wheel for all supported Python versions (3.9–3.14).

Changes

File	Change
tests/clients/test_sqlalchemy.py	postgresql:// → postgresql+psycopg2://
tests/requirements.txt	psycopg2-binary>=2.8.6 → >=2.9.12
tests/requirements-pre315.txt	psycopg2-binary>=2.8.6 → >=2.9.12

[pvital]

It looks good to me.