🔧 Fix frontend warnings and add diagnostic tools

Fix:
- Add type: module to package.json to eliminate ES module warning
- Create separate backend/frontend startup scripts
- Add system status check tool

New files:
- check_status.bat: Diagnose system status
- start_backend_only.bat: Start backend separately
- start_frontend_only.bat: Start frontend separately

🚀 Generated with [Claude Code](https://claude.com/claude-code)

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

frontend/package.json

@@ -1,6 +1,7 @@
 {
   "name": "qquiz-frontend",
   "version": "1.0.0",
+  "type": "module",
   "description": "QQuiz Frontend - React Application",
   "private": true,
   "dependencies": {