fix(nav): 하단 배너 데스크톱(768px+)에서 숨김 처리

모바일 전용 하단 네비가 데스크톱에서 본문과 겹치는 문제.
768px 이상에서 display:none, 480-767px에서 max-width 제한.

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

system1-factory/web/pages/purchase/request.html

@@ -6,7 +6,7 @@
     <title>소모품 신청 - TK 공장관리</title>
     <script src="https://cdn.tailwindcss.com"></script>
     <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.4.0/css/all.min.css">
-    <link rel="stylesheet" href="/static/css/tkfb.css?v=2026033108">
+    <link rel="stylesheet" href="/static/css/tkfb.css?v=2026040103">
     <script src="https://cdn.jsdelivr.net/npm/heic2any@0.0.4/dist/heic2any.min.js"></script>
     <style>
       .item-dropdown { position: absolute; top: 100%; left: 0; right: 0; max-height: 280px; overflow-y: auto; background: white; border: 1px solid #e5e7eb; border-top: none; border-radius: 0 0 8px 8px; box-shadow: 0 4px 12px rgba(0,0,0,0.1); z-index: 20; display: none; }