Two-tier layout with header, main content, and sidebar

This layout uses Tailwind CSS classes to create a two-tier structure with a header, main content area, and sidebar. The header has a responsive navigation menu, search bar, and user menu. The main content is split into two columns, with a wider column for the main details and notes, and a narrower sidebar for the timeline. The Tailwind classes handle the responsive styling for a clean layout on mobile and desktop.