fix: add invoke method to window.__TAURI_INTERNALS__ mock

Author: Y-RyuZU

jest.setup.js

@@ -2,7 +2,9 @@ require('@testing-library/jest-dom')
 
 // Mock Tauri API
 global.window = global.window || {};
-global.window.__TAURI_INTERNALS__ = {};
+global.window.__TAURI_INTERNALS__ = {
+  invoke: jest.fn()
+};
 global.window.isTauri = true;
 
 // Mock Tauri invoke function