🐛 Implement comprehensive error handling and user feedback mechanisms

[suwubh]

🎯 Fixes Issue #1

This PR implements comprehensive error handling and user feedback mechanisms as requested in #1.

✅ Changes Made

Error Handling:

• ✅ Added React Error Boundaries using react-error-boundary
• ✅ Implemented try-catch blocks for all async functions
• ✅ Created centralized API error handling via api.js service
• ✅ Added network connectivity error handling with axios interceptors

User Feedback:

• ✅ Replaced all browser alerts with toast notifications using react-hot-toast
• ✅ Added loading spinners for all async operations
• ✅ Implemented proper success/error messages for all user actions
• ✅ Created ConfirmDialog component for destructive actions

Form Validation:

• ✅ Added real-time validation with inline error messages
• ✅ Implemented loading states that prevent multiple submissions
• ✅ Added form validation feedback in SubjectCard name editing

🗂️ New Files Created

frontend/src/
├── utils/toast.js # Toast notification utilities
├── services/api.js # Centralized API service with error handling
├── components/ui/
│ ├── LoadingSpinner.jsx # Reusable loading spinner component
│ └── ConfirmDialog.jsx # Confirmation dialog for destructive actions
└── hooks/useFormValidation.js # Form validation hook (ready for future use)

🔧 Files Modified

• App.jsx - Added Toaster provider and enhanced ErrorBoundary
• AuthContext.jsx - Updated to use API service with proper error handling
• Dashboard.jsx - Replaced axios with API service, added toast notifications
• SubjectCard.jsx - Enhanced with comprehensive error handling, validation, and ConfirmDialog
• Login.jsx - Added API service, toast notifications, and loading states
• Register.jsx - Added API service, toast notifications, and loading states
• AddSubject.jsx - Added API service, toast notifications, and loading states
• Leaderboard.jsx - Added API service and error handling
• ErrorBoundary.jsx - Enhanced with better error UI and recovery options

📦 Dependencies Added

{
"react-hot-toast": "^2.4.1",
"react-error-boundary": "^4.0.11"
}

🧪 Testing Completed

• ✅ All forms now show proper loading states
• ✅ Error scenarios display appropriate toast messages
• ✅ Network errors are handled gracefully
• ✅ Form validation prevents invalid submissions
• ✅ Destructive actions require confirmation
• ✅ No more browser alerts anywhere in the app
• ✅ Error boundaries catch and display JS errors properly

🎯 Acceptance Criteria Met

• ✅ All API calls have error handling
• ✅ Loading states implemented app-wide
• ✅ Toast notifications for all user actions
• ✅ Error boundaries catch JS errors
• ✅ Form validation provides clear feedback
• ✅ No more browser alerts
• ✅ Confirmation dialogs for destructive actions

Conclusion

The app now provides a smooth user experience with:

• Beautiful toast notifications for all actions
• Loading spinners during async operations
• Proper error recovery and user guidance
• Confirmation dialogs for important actions
• Real-time form validation feedback

🚀 Ready for Review

This PR fully addresses all requirements in Issue #1 and implements modern error handling and user feedback patterns.

[suwubh]

Hi! I've created a pull request that addresses all the requirements in this issue.

PR Link: PR by suwubh

I've implemented:
✅ React Error Boundaries
✅ Toast notifications replacing all browser alerts
✅ Centralized API error handling
✅ Loading states for all async operations
✅ Form validation with real-time feedback
✅ Confirmation dialogs for destructive actions

The app now provides comprehensive error handling and user feedback as requested. Ready for review! 🚀