Bump playkit to v0.3 and use Zod API schemas

Adopt assertSchema via ApiClient, playkitFailureArtifacts in Playwright
config, and keep e2e login on e2e@levkine.ca credentials from CI secrets.

e2e/tests/api.health.spec.ts

@@ -1,10 +1,13 @@
+import { z } from 'zod';
 import { test, expect } from '../fixtures';
 
+const HealthSchema = z.object({ status: z.literal('ok') });
+
 test.describe('api @smoke', () => {
   test('backend /health returns ok', async ({ api, timings }) => {
     const res = await timings.measure('api_health', () =>
-      api.get<{ status: string }>('/health', { expectedStatus: 200 }),
+      api.get('/health', { expectedStatus: 200, schema: HealthSchema }),
     );
-    expect(res.data).toMatchObject({ status: 'ok' });
+    expect(res.data).toEqual({ status: 'ok' });
   });
 });