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/InlineItemCreate.tsx

@@ -4,6 +4,7 @@ import { useState } from 'react'
 import { useRouter } from 'next/navigation'
 import { createItem } from '@/lib/actions'
 import { Plus } from 'lucide-react'
+import { useToast } from './ToastContainer'
 
 interface InlineItemCreateProps {
   listId: string
@@ -11,6 +12,7 @@ interface InlineItemCreateProps {
 
 export default function InlineItemCreate({ listId }: InlineItemCreateProps) {
   const router = useRouter()
+  const { showToast } = useToast()
   const [isCreating, setIsCreating] = useState(false)
   const [title, setTitle] = useState('')
   const [isSubmitting, setIsSubmitting] = useState(false)
@@ -26,11 +28,13 @@ export default function InlineItemCreate({ listId }: InlineItemCreateProps) {
 
     try {
       await createItem(listId, title.trim())
+      showToast('Task added successfully', 'success')
       setTitle('')
       setIsCreating(false)
       router.refresh()
     } catch (error) {
       console.error('Error creating item:', error)
+      showToast('Failed to add task', 'error')
     } finally {
       setIsSubmitting(false)
     }