Implement hybrid print preview with CSS-based approach

- Add hidden print-preview-copy div at app level for clean print isolation
- Use @media print rules to show only print copy (960x720) in landscape
- Auto-sync print copy with preview content on modal render via use_effect
- Copy CSS variables and data attributes for proper hour filtering
- Set explicit dimensions matching print-preview-paper content area
- Force landscape orientation with @page rule for better calendar printing

🤖 Generated with [Claude Code](https://claude.ai/code)

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

frontend/index.html

@@ -6,7 +6,6 @@
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <base data-trunk-public-url />
     <link data-trunk rel="css" href="styles.css">
-    <link data-trunk rel="css" href="print.css">
     <link data-trunk rel="css" href="print-preview.css">
     <link data-trunk rel="copy-file" href="styles/google.css">
     <link data-trunk rel="icon" href="favicon.ico">