fix(monthly-comparison): showToast 재귀 + vacation diff + 주말 0h

- showToast: 로컬 함수 제거 → tkfb-core.js 전역 함수 사용 (재귀 무한루프 수정)
- vacation 상태에서도 hours_diff 표시 (반차 8h/4h → 차이: +4h)
- 주말 + 0h 근태 → 근태 행 숨김 (주말로만 표시)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

system1-factory/web/pages/attendance/monthly-comparison.html

@@ -164,7 +164,7 @@
 
     <script src="/static/js/tkfb-core.js?v=2026033108"></script>
     <script src="/js/api-base.js?v=2026031701"></script>
-    <script src="/js/monthly-comparison.js?v=2026040107"></script>
+    <script src="/js/monthly-comparison.js?v=2026040108"></script>
     <script>initAuth();</script>
 </body>
 </html>