test: playkit v0.3.1 network monitors, authed filters, admin-frontend Vitest

Bump @levkin/playkit to v0.3.1 (network interception helpers) and land the
work it unblocked: startNetworkErrorMonitor on gallery/search/upload/manage-
users, Favorites + People filter UI e2e (storageState), and a fix for the
lingering `res.data: unknown` / Mailpit-vs-Mailtrap type errors in the mail
and catalog specs. Also adds Vitest coverage + a CI job for admin-frontend,
which had no test infra before this.

admin-frontend/vitest.config.ts

@@ -0,0 +1,10 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    environment: 'node',
+    globals: true,
+    include: ['src/**/*.test.{ts,tsx}'],
+    exclude: ['node_modules', 'dist'],
+  },
+});