- Install sonner package for toast notifications
- Add Toaster component to root layout with dark theme styling
- Replace all alert() calls with toast.success() and toast.error()
- Add descriptive messages for success states
- Toast notifications match the app's dark theme design
- Add SQL seed data for trainers and collections
- Fix React hydration warning with suppressHydrationWarning
- Add empty state UI with friendly messaging
- Add error state UI with retry functionality
- Link Add Trainer buttons to /trainers/new page