Add initial work from Codex

backend/app/db/engine.py

@@ -0,0 +1,34 @@
+from __future__ import annotations
+
+from sqlalchemy import create_engine, event
+from sqlalchemy.engine import Engine
+
+from app.core.config import settings
+
+
+def _create_read_only_engine(connection_url: str) -> Engine:
+    engine = create_engine(
+        connection_url, pool_pre_ping=True, pool_recycle=3600, future=True
+    )
+
+    @event.listens_for(engine, "connect")
+    def _on_connect(dbapi_connection, _connection_record) -> None:
+        cursor = dbapi_connection.cursor()
+        try:
+            cursor.execute("SET TRANSACTION ISOLATION LEVEL READ COMMITTED;")
+        finally:
+            cursor.close()
+
+    return engine
+
+
+def create_warehouse_engines() -> dict[str, Engine]:
+    return {
+        "wwi": _create_read_only_engine(settings.wwi_connection_url),
+        "aw": _create_read_only_engine(settings.aw_connection_url),
+    }
+
+
+def dispose_engines(engines: dict[str, Engine]) -> None:
+    for engine in engines.values():
+        engine.dispose()