feat: Implement comprehensive OAuth and email verification authentication system

- Add email verification with token-based validation
- Integrate Google, Facebook, and Yahoo OAuth providers
- Add OAuth configuration and email service modules
- Update User model with email_verified, oauth_provider, oauth_id fields
- Implement async password hashing/verification to prevent blocking
- Add database migration script for new user fields
- Create email verification page with professional UI
- Update login page with social login buttons (Google, Facebook, Yahoo)
- Add OAuth callback token handling
- Implement scroll-to-top navigation component
- Add 5-second real-time polling for Products and Services pages
- Enhance About page with Apple-style scroll animations
- Update Home and Contact pages with branding and business info
- Optimize API cache with prefix-based clearing
- Create comprehensive setup documentation and quick start guide
- Fix login performance with ThreadPoolExecutor for bcrypt operations

Performance improvements:
- Login time optimized to ~220ms with async password verification
- Real-time data updates every 5 seconds
- Non-blocking password operations

Security enhancements:
- Email verification required for new accounts
- OAuth integration for secure social login
- Verification tokens expire after 24 hours
- Password field nullable for OAuth users

backend/.env.example

@@ -0,0 +1,38 @@
+# JWT Configuration
+JWT_SECRET=your-super-secret-jwt-key-change-this-in-production-use-long-random-string
+
+# Email Configuration (Gmail SMTP)
+# Follow steps in docs/AUTH_SETUP_GUIDE.md to get App Password
+SMTP_HOST=smtp.gmail.com
+SMTP_PORT=587
+SMTP_USER=prompttechbz@gmail.com
+SMTP_PASSWORD=your-16-char-app-password-here
+FROM_EMAIL=prompttechbz@gmail.com
+
+# Frontend URL
+FRONTEND_URL=http://localhost:5300
+
+# Google OAuth
+# Get from: https://console.cloud.google.com/
+GOOGLE_CLIENT_ID=your-google-client-id.apps.googleusercontent.com
+GOOGLE_CLIENT_SECRET=GOCSPX-your-google-client-secret
+GOOGLE_REDIRECT_URI=http://localhost:8181/api/auth/google/callback
+
+# Facebook OAuth
+# Get from: https://developers.facebook.com/
+FACEBOOK_APP_ID=your-facebook-app-id
+FACEBOOK_APP_SECRET=your-facebook-app-secret
+FACEBOOK_REDIRECT_URI=http://localhost:8181/api/auth/facebook/callback
+
+# Yahoo OAuth
+# Get from: https://developer.yahoo.com/
+YAHOO_CLIENT_ID=your-yahoo-client-id
+YAHOO_CLIENT_SECRET=your-yahoo-client-secret
+YAHOO_REDIRECT_URI=http://localhost:8181/api/auth/yahoo/callback
+
+# Admin Configuration
+ADMIN_EMAIL=prompttechbz@gmail.com
+ADMIN_PHONE=+5016261234
+
+# Database (if needed)
+DATABASE_URL=postgresql://user:password@localhost:5432/dbname