Use skipLibCheck for backend build in CI

Work around TypeScript version mismatch with @types/babel__traverse
by skipping library type checking.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Laoujin

.github/workflows/playwright.yml

@@ -67,7 +67,7 @@ jobs:
 
       - name: Build backend
         working-directory: ./confac/backend
-        run: npm run build
+        run: npx tsc -p . --skipLibCheck
 
       - name: Start backend
         working-directory: ./confac/backend