feat: Add visual feedback and polish (Task 15)

- Implement toast notification system for success/error messages
- Add loading states with skeleton loaders for async operations
- Create smooth CSS transitions and animations
- Enhance empty states with EmptyState component
- Add loading.tsx files for Next.js loading states
- Integrate toast notifications across all CRUD operations
- Add fade-in and scale-in animations for better UX
- Improve visual feedback for user actions

components/Modal.tsx

@@ -42,15 +42,15 @@ export default function Modal({ isOpen, onClose, title, children }: ModalProps)
   if (!isOpen) return null
 
   return (
-    <div className="fixed inset-0 z-50 flex items-end sm:items-center justify-center">
+    <div className="fixed inset-0 z-50 flex items-end sm:items-center justify-center animate-fade-in">
       {/* Backdrop */}
       <div 
-        className="absolute inset-0 bg-black bg-opacity-50 transition-opacity"
+        className="absolute inset-0 bg-black bg-opacity-50 transition-opacity backdrop-blur-sm"
         onClick={onClose}
       />
       
       {/* Modal */}
-      <div className="relative bg-white rounded-t-2xl sm:rounded-lg shadow-xl max-w-md w-full mx-0 sm:mx-4 max-h-[90vh] overflow-y-auto transform transition-transform">
+      <div className="relative bg-white rounded-t-2xl sm:rounded-lg shadow-xl max-w-md w-full mx-0 sm:mx-4 max-h-[90vh] overflow-y-auto transform transition-transform animate-scale-in">
         <div className="flex items-center justify-between p-4 sm:p-5 border-b border-gray-200 sticky top-0 bg-white z-10">
           <h2 className="text-lg sm:text-xl font-semibold text-gray-900">{title}</h2>
           <button