feat: add foreign key constraints and metrics for blockchain node

apps/blockchain-node/tests/conftest.py

@@ -0,0 +1,23 @@
+from __future__ import annotations
+
+import pytest
+from sqlmodel import SQLModel, Session, create_engine
+
+from aitbc_chain.models import Block, Transaction, Receipt  # noqa: F401 - ensure models imported for metadata
+
+
+@pytest.fixture(name="engine")
+def engine_fixture():
+    engine = create_engine("sqlite:///:memory:", connect_args={"check_same_thread": False})
+    SQLModel.metadata.create_all(engine)
+    try:
+        yield engine
+    finally:
+        SQLModel.metadata.drop_all(engine)
+
+
+@pytest.fixture(name="session")
+def session_fixture(engine):
+    with Session(engine) as session:
+        yield session
+        session.rollback()