Add integration tests for execution persistence, metrics, and opportunity writing

- Implemented integration tests for the execution writer to ensure trade orders and PnL are persisted correctly.
- Created integration tests for the metrics calculator to summarize execution data accurately.
- Added integration tests for the opportunity writer to verify event persistence.
- Established PostgreSQL schema validation tests to ensure all expected tables, columns, and constraints exist.
- Removed outdated unit tests that relied on DuckDB and replaced them with tests using PgStore.

tests/integration/test_audit_repository.py

@@ -0,0 +1,52 @@
+from __future__ import annotations
+
+from collections.abc import AsyncIterator
+from contextlib import asynccontextmanager
+from datetime import UTC, datetime
+
+import pytest
+import pytest_asyncio
+
+from arbitrade.config.settings import get_settings
+from arbitrade.storage.pg_store import PgStore
+from arbitrade.storage.repositories import AuditRecord, AuditRepository
+
+pytestmark = pytest.mark.integration
+
+
+@asynccontextmanager
+async def _pg() -> AsyncIterator[PgStore]:
+    s = get_settings()
+    store = PgStore(s)
+    try:
+        await store.start()
+        await store.migrate()
+        yield store
+    finally:
+        await store.stop()
+
+
+@pytest.mark.asyncio
+async def test_audit_repository_inserts_and_lists_recent() -> None:
+    async with _pg() as store:
+        repository = AuditRepository(store)
+
+        await repository.insert(
+            AuditRecord(
+                occurred_at=datetime.now(UTC),
+                actor="dashboard_user",
+                event_type="dashboard.control.start",
+                decision="approved",
+                payload={"execution_status": "running"},
+                correlation_id="req-1",
+            )
+        )
+
+        recent = await repository.list_recent(limit=5)
+
+        assert len(recent) == 1
+        assert recent[0].actor == "dashboard_user"
+        assert recent[0].event_type == "dashboard.control.start"
+        assert recent[0].decision == "approved"
+        assert recent[0].payload == {"execution_status": "running"}
+        assert recent[0].correlation_id == "req-1"