feat: enhance mock database store with context manager support and improve cursor behavior

tests/unit/test_config_service.py

@@ -20,8 +20,17 @@ def mock_settings():
 
 @pytest.fixture
 def mock_store():
-    """Create a mock database store."""
+    """Create a mock database store with context manager support."""
     store = Mock(spec=DuckDBStore)
+    cursor = Mock()
+    cursor.fetchone.return_value = None
+    cursor.fetchall.return_value = []
+    cursor.execute.return_value = cursor
+    # Set up context manager via mock_connect property
+    store.connect.side_effect = None  # disable side effect
+    context_mock = Mock()
+    context_mock.__enter__.return_value = cursor
+    store.connect.return_value = context_mock
     return store