feat(frontend): implement core UI components and workflow integration

This commit completes the essential frontend components with full backend integration:

## Core UI Components ✅
- FileUpload component with drag & drop, validation, and progress tracking
- ProgressTracker component with real-time WebSocket updates and batch monitoring
- Complete landing page sections (Hero, Features, How It Works, Pricing)
- Dashboard component for authenticated users
- WorkflowSection for guided image processing workflow

## Authentication & Pages ✅
- OAuth callback page with error handling and loading states
- Complete authentication flow with redirect management
- Proper error boundaries and user feedback systems
- Toast notification system with multiple variants

## Environment & Configuration ✅
- Environment variable setup for development and production
- Complete .env.example with all required variables
- Comprehensive README with setup and integration instructions
- Development and deployment guidelines

## Integration Features ✅
- Real-time progress tracking via WebSocket connections
- File upload with validation, progress, and error handling
- Complete authentication flow with Google OAuth
- API client integration with all backend endpoints
- Error handling and loading states throughout the application

## User Experience ✅
- Responsive design with mobile-first approach
- Dark mode support with proper theme management
- Comprehensive error handling with user-friendly messages
- Loading spinners and progress indicators
- Professional UI components with proper accessibility

## Technical Architecture ✅
- Next.js 14 App Router with TypeScript
- Complete Tailwind CSS design system
- Custom hooks for authentication, upload, and WebSocket
- Type-safe API client with comprehensive error handling
- Modular component architecture with proper separation

This provides a complete, production-ready frontend that seamlessly integrates with the existing backend APIs and supports the full user workflow from authentication to image processing and download.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

packages/frontend/.env.example

@@ -0,0 +1,18 @@
+# Frontend Environment Variables
+
+# API Configuration
+NEXT_PUBLIC_API_URL=http://localhost:3001
+NEXT_PUBLIC_WS_URL=ws://localhost:3001
+
+# Authentication
+NEXT_PUBLIC_GOOGLE_CLIENT_ID=your-google-client-id.apps.googleusercontent.com
+
+# Stripe Configuration
+NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY=pk_test_your_stripe_publishable_key
+
+# Feature Flags
+NEXT_PUBLIC_ENABLE_ANALYTICS=false
+NEXT_PUBLIC_ENABLE_DEBUG=false
+
+# Environment
+NODE_ENV=development