feat: Implement dark mode theme and improve UI

- Add CSS variables for theming
- Implement dark mode toggle functionality
- Refactor styles for better organization and readability
- Update navigation bar with theme toggle button
- Enhance hero section with display-4 font size
- Adjust card styles for consistent appearance
- Improve alert and badge styling
- Make hero server title bold and larger
- Use Bootstrap 5 classes for consistent styling
- Add prefetch for Bootstrap JS
- Update `auth_enabled` default to false in server creation

examples/hero/heroserver/heroserver.vsh

@@ -5,7 +5,7 @@ import incubaid.herolib.schemas.openrpc
 import os
 
 // 1. Create a new server instance
-mut server := heroserver.new(port: 8080)!
+mut server := heroserver.new(port: 8080, auth_enabled: false)!
 
 // 2. Create and register your OpenRPC handlers
 //    These handlers must conform to the `openrpc.OpenRPCHandler` interface.