chore: 优化密码库前端界面与样式

mengyakeyvault-frontend/public/offline.html

@@ -5,10 +5,12 @@
   <meta name="viewport" content="width=device-width, initial-scale=1" />
   <meta name="theme-color" content="#4caf50" />
   <title>离线 - 萌芽密码管理器</title>
+  <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/lxgw-wenkai-webfont@1.7.0/lxgwwenkaimono-regular.css" />
+  <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/lxgw-wenkai-webfont@1.7.0/lxgwwenkaimono-bold.css" />
   <style>
     * { box-sizing: border-box; margin: 0; padding: 0; }
     body {
-      font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
+      font-family: 'LXGW WenKai Mono', ui-monospace, monospace;
       background: linear-gradient(135deg, #f0fdf0 0%, #e8f5e9 100%);
       min-height: 100vh;
       display: flex;
@@ -29,6 +31,7 @@
     h1 { font-size: 22px; color: #1b5e20; margin-bottom: 12px; font-weight: 700; }
     p { font-size: 15px; color: #666; line-height: 1.6; margin-bottom: 24px; }
     button {
+      font-family: inherit;
       background: linear-gradient(135deg, #66bb6a, #4caf50);
       color: #fff;
       border: none;