Use vitest for some EW unit tests (#33816)

* Use vitest for some EW unit tests

* Ensure library builds are done before unit tests

* Stabilise jest tests

* Move more tests over

* Make sonar happier

* Update types/node for happy-dom compat again

* Decrease max-workers to stabilise jest tests

* Split jest over 3 runners to alleviate memory woes

* Switch jest to runInBand

* Attempt to deflake jest tests

* tweak coverage

* tweak coverage

apps/web/src/test/setupTests.ts

@@ -0,0 +1,18 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import { beforeEach } from "vitest";
+import fetchMock, { manageFetchMockGlobally } from "@fetch-mock/vitest";
+
+manageFetchMockGlobally();
+
+beforeEach(() => {
+    // set up fetch API mock
+    fetchMock.hardReset();
+    fetchMock.catch(404);
+    fetchMock.mockGlobal();
+});