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>

frontend/lib/auth.ts

@@ -0,0 +1,29 @@
+export function saveAuth(token: string, user: any) {
+  localStorage.setItem('token', token);
+  localStorage.setItem('user', JSON.stringify(user));
+}
+
+export function getAuth() {
+  if (typeof window === 'undefined') return null;
+
+  const token = localStorage.getItem('token');
+  const userStr = localStorage.getItem('user');
+
+  if (!token || !userStr) return null;
+
+  try {
+    const user = JSON.parse(userStr);
+    return { token, user };
+  } catch {
+    return null;
+  }
+}
+
+export function clearAuth() {
+  localStorage.removeItem('token');
+  localStorage.removeItem('user');
+}
+
+export function isAuthenticated() {
+  return !!getAuth();
+}