feat: implement notification center UI with dropdown and full history…

[Delightech28]

Pull Request: Notification Center UI (#119)

📋 Description

Implements a complete notification center system allowing users to view, manage, and interact with system and contract-related events. Includes a dropdown panel in the dashboard header and a dedicated full-page notification history view.

✨ Features

Notification Dropdown

• Accessible from the navbar bell icon
• Shows 10 most recent notifications with pagination
• Real-time unread badge count (updates every 10 seconds)
• Quick actions to mark as read/unread and delete
• "View All Notifications" link to full history page
• Loading and empty states

Full-Page Notification History (/dashboard/notifications)

• Paginated list with 20 items per page
• Filter by: All, Unread, Read
• Full notification details with timestamps
• Bulk actions and individual item controls
• Responsive layout for all device sizes

Real-time Updates

• Polling-based unread count (10-second intervals)
• Dynamic badge display (shows count or "99+")
• Auto-refresh when panel is closed

Notification Types

• Milestone Approved ✓
• Funds Released 💰
• Contract Created 📋
• Dispute Raised ⚠️
• Escrow Funded 🔒
• Payment Released ✓

🔧 Technical Details

New Files Created

Service Layer

• lib/notifications.ts — Notification database operations
  • listNotifications() — Paginated list with filters
  • countNotifications() — Count notifications
  • getUnreadCount() — Get unread badge count
  • markAsRead() / markAsUnread() — Toggle read status
  • markAllAsRead() — Bulk operation
  • deleteNotification() — Delete notification
  • createNotification() — Create new notification

API Endpoints

• app/api/notifications/route.ts — List and mark all as read
• app/api/notifications/[id]/route.ts — Update/delete individual notifications
• app/api/notifications/unread-count/route.ts — Get unread count

UI Components

• components/dashboard/notification-item.tsx — Individual notification card
• components/dashboard/notification-panel.tsx — Dropdown panel
• app/dashboard/notifications/page.tsx — Full history page
• app/dashboard/notifications/notifications-client.tsx — Page client component

Modified Files

• components/dashboard/header.tsx — Added notification bell icon with panel integration

🎯 Acceptance Criteria Met

• ✅ Users can mark notifications as read/unread
• ✅ Unread badge count updates dynamically in real time
• ✅ Pagination supported for long notification lists
• ✅ Responsive UI across devices (mobile, tablet, desktop)
• ✅ Notifications displayed with proper timestamp and type icon
• ✅ Loading states shown during API calls
• ✅ Empty state displayed when no notifications exist
• ✅ Notification dropdown accessible from navbar/avatar
• ✅ Dedicated notification page for full history view

🔐 Security & Performance

• Rate-limited API endpoints (60 req/min for list, 30 req/min for updates)
• Authentication required via withAuth middleware
• User-owned notification validation
• Efficient database queries with indexes
• Pagination to prevent large data transfers
• Polling interval set to 10 seconds to balance UX and server load

🧪 Testing Recommendations

• Test notification dropdown open/close
• Verify real-time badge count updates
• Test mark as read/unread functionality
• Test delete notification
• Test pagination in both dropdown and full page
• Test filter tabs on full page
• Test responsive design on mobile/tablet/desktop
• Test error states and empty states
• Verify API rate limiting works correctly
• Check that only user's own notifications are visible

📱 UI/UX Highlights

• Color-coded notification types for quick visual scanning
• Smooth animations and hover states
• Mobile-optimized dropdown (96vw max width)
• Clear pagination indicators
• Helpful empty state messages based on filter
• Action buttons reveal on hover (except mobile where always visible)

🚀 Deployment Notes

• Database migration already exists (lib/db/migrations/001_taskchain_schema.sql)
• No new environment variables required
• Existing auth middleware handles security
• Rate limiting already configured in security module

📝 Related Issues

Closes #119

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[SudiptaPaul-31]

@Delightech28 fix build