Add modern UI with glassmorphism and gradients (v1.7.1)

- Created comprehensive modern CSS design system
- Glassmorphism effects with backdrop-filter blur
- Animated purple-blue gradient background
- Modern Inter and JetBrains Mono typography
- Smooth transitions and hover effects
- Enhanced tab, button, and dialog styling
- Custom scrollbars and progress bars
- CSS custom properties for consistent theming
🤖 Generated with [Claude Code](https://claude.com/claude-code)

src/index.html

@@ -4,7 +4,11 @@
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>PanConverter - Markdown Editor</title>
+    <link rel="preconnect" href="https://fonts.googleapis.com">
+    <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
+    <link href="https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=JetBrains+Mono:wght@400;500;600&display=swap" rel="stylesheet">
     <link rel="stylesheet" href="styles.css">
+    <link rel="stylesheet" href="styles-modern.css">
     <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/codemirror/6.65.7/codemirror.min.css">
     <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/styles/default.min.css">
 </head>