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

app/globals.css

@@ -30,6 +30,57 @@ mark {
   }
 }
 
+/* Animations for visual feedback */
+@layer utilities {
+  @keyframes slide-in-right {
+    from {
+      transform: translateX(100%);
+      opacity: 0;
+    }
+    to {
+      transform: translateX(0);
+      opacity: 1;
+    }
+  }
+  
+  @keyframes fade-in {
+    from {
+      opacity: 0;
+    }
+    to {
+      opacity: 1;
+    }
+  }
+  
+  @keyframes scale-in {
+    from {
+      transform: scale(0.95);
+      opacity: 0;
+    }
+    to {
+      transform: scale(1);
+      opacity: 1;
+    }
+  }
+  
+  .animate-slide-in-right {
+    animation: slide-in-right 0.3s ease-out;
+  }
+  
+  .animate-fade-in {
+    animation: fade-in 0.2s ease-out;
+  }
+  
+  .animate-scale-in {
+    animation: scale-in 0.2s ease-out;
+  }
+  
+  /* Smooth transitions for interactive elements */
+  .transition-smooth {
+    transition: all 0.2s ease-in-out;
+  }
+}
+
 /* Smooth scrolling for better mobile experience */
 @layer base {
   html {