test: vitest setup + auth/login/cookie banner tests

DataSentinel/src/test/setup.js

@@ -0,0 +1,7 @@
+/* Configuration globale des tests : matchers jest-dom + nettoyage du localStorage */
+import '@testing-library/jest-dom';
+import { afterEach } from 'vitest';
+
+afterEach(() => {
+  localStorage.clear();
+});