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/Trunk.toml

@@ -6,7 +6,7 @@ dist = "dist"
 BACKEND_API_URL = "http://localhost:3000/api"
 
 [watch]
-watch = ["src", "Cargo.toml", "../calendar-models/src", "styles.css", "print.css", "print-preview.css", "index.html"]
+watch = ["src", "Cargo.toml", "../calendar-models/src", "styles.css", "print-preview.css", "index.html"]
 ignore = ["../backend/", "../target/"]
 
 [serve]