Initial implementation of Website Change Detection Monitor MVP

Features implemented:
- Backend API with Express + TypeScript
- User authentication (register/login with JWT)
- Monitor CRUD operations with plan-based limits
- Automated change detection engine
- Email alert system
- Frontend with Next.js + TypeScript
- Dashboard with monitor management
- Login/register pages
- Monitor history viewer
- PostgreSQL database schema
- Docker setup for local development

Technical stack:
- Backend: Express, TypeScript, PostgreSQL, Redis (ready)
- Frontend: Next.js 14, React Query, Tailwind CSS
- Database: PostgreSQL with migrations
- Services: Page fetching, diff detection, email alerts

Documentation:
- README with full setup instructions
- SETUP guide for quick start
- PROJECT_STATUS with current capabilities
- Complete technical specifications

Ready for local testing and feature expansion.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

backend/.env.example

@@ -0,0 +1,32 @@
+# Server
+PORT=3001
+NODE_ENV=development
+
+# Database
+DATABASE_URL=postgresql://user:password@localhost:5432/website_monitor
+
+# Redis
+REDIS_URL=redis://localhost:6379
+
+# JWT
+JWT_SECRET=your-super-secret-jwt-key-change-this-in-production
+JWT_EXPIRES_IN=7d
+
+# Email (Sendgrid/SMTP)
+EMAIL_FROM=noreply@websitemonitor.com
+SMTP_HOST=smtp.sendgrid.net
+SMTP_PORT=587
+SMTP_USER=apikey
+SMTP_PASS=your-sendgrid-api-key
+
+# App
+APP_URL=http://localhost:3000
+API_URL=http://localhost:3001
+
+# Rate Limiting
+MAX_MONITORS_FREE=5
+MAX_MONITORS_PRO=50
+MAX_MONITORS_BUSINESS=200
+MIN_FREQUENCY_FREE=60
+MIN_FREQUENCY_PRO=5
+MIN_FREQUENCY_BUSINESS=1