fix(ux): 데스크탑 UX 일괄 개선 — fade-in·ESC·스크롤잠금·z-index·sticky

A1: fade-in querySelectorAll 전환 (5개 core.js) — 복수 요소 모두 표시
A2: 모달 ESC 키 닫기 (5개 core.js)
A3: 모바일 메뉴 body 스크롤 잠금 (tkfb-core.js)
A4: Gateway 대시보드 max-width 800→1080px
B1: 모달 z-index 50→60 — 헤더 위에 표시 (4개 CSS)
B3: 테이블 sticky header (tkfb.css, tkpurchase.css)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tksafety/web/static/css/tksafety.css

@@ -47,7 +47,7 @@ body { font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif; b
 .collapsible-content.open { max-height: 500px; }
 
 /* Modal */
-.modal-overlay { position: fixed; inset: 0; background: rgba(0,0,0,0.4); display: flex; align-items: center; justify-content: center; z-index: 50; padding: 1rem; }
+.modal-overlay { position: fixed; inset: 0; background: rgba(0,0,0,0.4); display: flex; align-items: center; justify-content: center; z-index: 60; padding: 1rem; }
 .modal-content { background: white; border-radius: 0.75rem; max-width: 40rem; width: 100%; max-height: 90vh; overflow-y: auto; box-shadow: 0 20px 60px rgba(0,0,0,0.2); }
 
 /* Safety warning */

tksafety/web/static/js/tksafety-core.js

@@ -140,7 +140,7 @@ function initAuth() {
     // 알림 벨 로드
     _loadNotificationBell();
 
-    setTimeout(() => document.querySelector('.fade-in')?.classList.add('visible'), 50);
+    setTimeout(() => document.querySelectorAll('.fade-in').forEach(el => el.classList.add('visible')), 50);
     return true;
 }
 
@@ -150,3 +150,11 @@ function _loadNotificationBell() {
     s.src = (location.hostname.includes('technicalkorea.net') ? 'https://tkds.technicalkorea.net' : location.protocol + '//' + location.hostname + ':30000') + '/shared/notification-bell.js?v=3';
     document.head.appendChild(s);
 }
+
+/* ===== Modal ESC 닫기 ===== */
+document.addEventListener('keydown', e => {
+    if (e.key === 'Escape') {
+        document.querySelectorAll('.modal-overlay:not(.hidden)')
+            .forEach(m => m.classList.add('hidden'));
+    }
+});