fix(ci): add tenant_id to health_metrics test insert, rollback before cleanup

- test_monitoring_api: health_metrics INSERT was missing tenant_id column
- conftest: rollback failed transactions before TRUNCATE cleanup

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/tests/integration/conftest.py

@@ -188,11 +188,13 @@ async def admin_session(admin_engine) -> AsyncGenerator[AsyncSession, None]:
         yield session
     finally:
         try:
+            # Rollback any failed transaction before cleanup
+            await session.rollback()
             if existing_tables:
                 await session.execute(text(f"TRUNCATE {tables_csv} CASCADE"))
                 await session.commit()
-        except RuntimeError:
-            pass  # Event loop may be closed during final teardown
+        except (RuntimeError, Exception):
+            pass  # Event loop may be closed or session in bad state
         await session.close()