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/src/routes/auth.ts

@@ -0,0 +1,143 @@
+import { Router, Request, Response } from 'express';
+import { z } from 'zod';
+import db from '../db';
+import {
+  hashPassword,
+  comparePassword,
+  generateToken,
+  validateEmail,
+  validatePassword,
+} from '../utils/auth';
+
+const router = Router();
+
+const registerSchema = z.object({
+  email: z.string().email(),
+  password: z.string().min(8),
+});
+
+const loginSchema = z.object({
+  email: z.string().email(),
+  password: z.string(),
+});
+
+// Register
+router.post('/register', async (req: Request, res: Response): Promise<void> => {
+  try {
+    const { email, password } = registerSchema.parse(req.body);
+
+    if (!validateEmail(email)) {
+      res.status(400).json({
+        error: 'invalid_email',
+        message: 'Invalid email format',
+      });
+      return;
+    }
+
+    const passwordValidation = validatePassword(password);
+    if (!passwordValidation.valid) {
+      res.status(400).json({
+        error: 'invalid_password',
+        message: 'Password does not meet requirements',
+        details: passwordValidation.errors,
+      });
+      return;
+    }
+
+    const existingUser = await db.users.findByEmail(email);
+    if (existingUser) {
+      res.status(409).json({
+        error: 'user_exists',
+        message: 'User with this email already exists',
+      });
+      return;
+    }
+
+    const passwordHash = await hashPassword(password);
+    const user = await db.users.create(email, passwordHash);
+
+    const token = generateToken(user);
+
+    res.status(201).json({
+      token,
+      user: {
+        id: user.id,
+        email: user.email,
+        plan: user.plan,
+        createdAt: user.createdAt,
+      },
+    });
+  } catch (error) {
+    if (error instanceof z.ZodError) {
+      res.status(400).json({
+        error: 'validation_error',
+        message: 'Invalid input',
+        details: error.errors,
+      });
+      return;
+    }
+
+    console.error('Register error:', error);
+    res.status(500).json({
+      error: 'server_error',
+      message: 'Failed to register user',
+    });
+  }
+});
+
+// Login
+router.post('/login', async (req: Request, res: Response): Promise<void> => {
+  try {
+    const { email, password } = loginSchema.parse(req.body);
+
+    const user = await db.users.findByEmail(email);
+    if (!user) {
+      res.status(401).json({
+        error: 'invalid_credentials',
+        message: 'Invalid email or password',
+      });
+      return;
+    }
+
+    const isValidPassword = await comparePassword(password, user.passwordHash);
+    if (!isValidPassword) {
+      res.status(401).json({
+        error: 'invalid_credentials',
+        message: 'Invalid email or password',
+      });
+      return;
+    }
+
+    await db.users.updateLastLogin(user.id);
+
+    const token = generateToken(user);
+
+    res.json({
+      token,
+      user: {
+        id: user.id,
+        email: user.email,
+        plan: user.plan,
+        createdAt: user.createdAt,
+        lastLoginAt: new Date(),
+      },
+    });
+  } catch (error) {
+    if (error instanceof z.ZodError) {
+      res.status(400).json({
+        error: 'validation_error',
+        message: 'Invalid input',
+        details: error.errors,
+      });
+      return;
+    }
+
+    console.error('Login error:', error);
+    res.status(500).json({
+      error: 'server_error',
+      message: 'Failed to login',
+    });
+  }
+});
+
+export default router;