Renders flash messages for the Dashboard.

Displays Phoenix flash messages (info, error) as notification bars inside the dashboard layout. Each flash kind gets a distinct CSS class for visual styling.

Renders the root layout HTML document.

Includes:

• HTML5 doctype and responsive viewport meta
• CSRF token and LiveSocket path metas for the LiveView client
• Versioned CSS and JS asset links
• Sidebar navigation with icons for Outbound, Inbound, and Cluster nodes
• Flash group rendering
• Main content area yielding @inner_content

The asset links and navigation hrefs are built from @mount_prefix so the dashboard works when mounted under a path prefix. When rendered outside the LiveView mount (e.g. in tests or with a custom :on_mount), @mount_prefix, @assets_path and @socket_path default to /, /dashboard-assets and /live respectively.