fix: block service worker in e2e tests to prevent response interception

Active service workers change the fetch lifecycle enough that Playwright's
waitForResponse() misses SW-mediated responses, causing preferences tests
to timeout. Block SW registration during e2e tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

playwright.config.ts

@@ -11,7 +11,8 @@ export default defineConfig({
 	use: {
 		baseURL: 'http://localhost:4173',
 		trace: 'on-first-retry',
-		screenshot: 'only-on-failure'
+		screenshot: 'only-on-failure',
+		serviceWorkers: 'block'
 	},
 	projects: [
 		{