Add Postgres table adapter with TableRepositoryInterface.

Introduce PostgresAdapter for dict-based row CRUD via psycopg3, including config, lazy exports, unit/integration tests with testcontainers, and an example UserTableRepository.

Co-authored-by: Cursor <[email protected]>

tests/integration/postgres/conftest.py

@@ -0,0 +1,33 @@
+"""Postgres integration test fixtures."""
+
+from collections.abc import Generator
+
+import psycopg
+import pytest
+
+from python_repositories.config import PostgresConfig
+from tests.integration.postgres._containers import (
+    postgres_config_from_container,
+    postgres_uri,
+    raw_postgres_client_from_container,
+)
+
+
+@pytest.fixture(scope="session")
+def postgres_container() -> Generator[str, None, None]:
+    """Set up a Postgres container for testing and yield the Postgres URI."""
+    yield from postgres_uri()
+
+
+@pytest.fixture(scope="session")
+def postgres_config(postgres_container: str) -> PostgresConfig:
+    """Provide PostgresConfig built from the test container."""
+    return postgres_config_from_container(postgres_container)
+
+
+@pytest.fixture(scope="session")
+def raw_postgres_client(
+    postgres_container: str,
+) -> Generator[psycopg.Connection, None, None]:
+    """Provide a raw Postgres client connected to the test container."""
+    yield from raw_postgres_client_from_container(postgres_container)