test: run tests with 2 workers for faster CI

47 tests with 1 worker exceeds CI timeout. 2 workers cuts
total execution time roughly in half.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

playwright.config.ts

@@ -8,7 +8,7 @@ export default defineConfig({
   testDir: './tests',
   testIgnore: ['**/admin_debug.spec.ts'],
   timeout: 120_000,
-  workers: 1,
+  workers: 2,
   expect: { timeout: 30_000 },
   use: {
     baseURL: