Integrate shadcn UI & add UI primitives

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.

package.json

@@ -30,7 +30,6 @@
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
     "react-router-dom": "^7.14.0",
-    "shadcn": "^4.2.0",
     "tailwind-merge": "^3.5.0",
     "tw-animate-css": "^1.4.0",
     "vite": "^6.2.0",
@@ -42,6 +41,7 @@
     "@vitest/ui": "^4.1.4",
     "autoprefixer": "^10.4.21",
     "jsdom": "^29.0.2",
+    "shadcn": "^4.5.0",
     "tailwindcss": "^4.1.14",
     "tsx": "^4.21.0",
     "typedoc": "^0.28.19",