- Update Pipfile dependencies to resolve compatibility issues
- Remove deprecated black config option (skip-numeric-underscore-normalization)
- Add E704 to flake8 ignore list for compatibility with black's stub formatting
- Fix type annotation in postgres_client.py: change params: dict = None to
  params: Optional[dict] = None to satisfy mypy's no_implicit_optional
- Apply black and isort formatting to existing files

All linting checks (flake8, mypy, black, isort) now pass.

- Update mock paths in test_postgres_handler.py from tentaclio.clients.postgres_client
  to tentaclio_postgres.clients.postgres_client (the correct module path for this
  plugin package)
- Update conftest.py to import tentaclio_postgres instead of using tentaclio.clients,
  since PostgresClient is not part of the base tentaclio package

All 13 unit tests now pass.

- Add docker-compose.yml for local PostgreSQL testing environment
- Add explicit db_client.conn.commit() calls after set_schema() and delete_schema()
  in test fixtures to ensure schema changes are visible to other database connections
- Add pytest.mark.skipif decorators to gracefully skip tests when PostgreSQL is not
  configured locally

Root cause: Schema changes (CREATE TABLE, DROP TABLE) were not being committed to the
database, so when tentaclio.open() created a new connection, it couldn't see the tables
created by the test fixture, causing "relation does not exist" errors.

All 15 functional tests now pass when run with local PostgreSQL via docker-compose.

- Update PostgreSQL connection string to include password authentication:
  postgresql://circleci:testpassword@localhost:5432/tentaclio-db
- Set POSTGRES_PASSWORD in postgres container environment
- Install postgresql-client in CI for database readiness checks
- Add wait-for-postgres step to ensure database is ready before running tests

The functional tests were timing out in CI because:
1. The connection string didn't include authentication credentials
2. Tests ran before PostgreSQL was fully initialized

With these changes, the functional tests run successfully in CI with proper
password authentication instead of relying on trust-based authentication.