Integrates the shadcn/ui design system across the app and adds a collection of reusable UI primitives and layout components. Adds new UI atoms/molecules (avatar, card, collapsible, progress, select, sheet, sidebar, skeleton, table, tabs, toggles, tooltip), app sidebar, media filters, MediaTable, and a mobile hook; updates many views/components to use the new UI. Updates AGENTS.md with styling, layout, accessibility and design standards (Tailwind/shadcn guidance) and adds a registry entry to components.json. Also updates dependencies/lockfile to align shadcn and related packages.
Lars Behrends