feat(06-03): Update Playwright config and tests to ES modules syntax

frontend/playwright.config.js

@@ -1,4 +1,4 @@
-module.exports = {
+export default {
   testDir: "./tests",
   use: {
     baseURL: process.env.STAGING_URL || "https://gravl.homelab.local",

frontend/tests/gravl.spec.js

@@ -1,4 +1,4 @@
-const { test, expect } = require("@playwright/test");
+import { test, expect } from "@playwright/test";
 
 test("login page loads", async ({ page }) => {
   await page.goto("/login");