Two Column Layout with Sidebar

This implements a two column layout with a sidebar on the right. It uses Tailwind's flexbox utilities to create a flex container with two child elements - the main content and the sidebar. The main content uses `flex-1` to take up remaining space. The sidebar is fixed width. On small screens the sidebar is hidden. The header uses Tailwind's border and background color utilities. The nav menu uses `space-y` and `flex` utilities to stack the menu items vertically. The main content section uses Grid with `grid-cols` to layout the gallery. The gallery images use `aspect` utilities to maintain aspect ratio. The sidebar shows details for a selected image. It uses `space-y` to space elements vertically.