Build LoadingSpinner, EmptyState & 404 Page. Create ErrorBoundary with retry and add Toaster QueryProvider and Devtools to App. - [ ] Reusable components accept common props and are exported from a barrel - [ ] ErrorBoundary catches render errors with Retry button - [ ] Toast system exposes success() and error() with Toaster component
Build LoadingSpinner, EmptyState & 404 Page. Create ErrorBoundary with retry and add Toaster QueryProvider and Devtools to App.