Add playwright E2E tests (#2174)

photon-client/tests/fixtures.ts

@@ -0,0 +1,16 @@
+import { test as base } from "@playwright/test";
+import axios from "axios";
+
+export const test = base.extend({
+  page: async ({ page }, use) => {
+    // Use the page in the test (no per-test backend reset here)
+    axios.defaults.baseURL = "http://localhost:5800/api/test";
+    await use(page);
+  }
+});
+
+test.beforeAll(async () => {
+  console.log("Running before all tests: Resetting backend state...");
+  await axios.post("http://localhost:5800/api/test/resetBackend");
+  await axios.post("http://localhost:5800/api/test/activateTestMode");
+});