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/requirements.txt

@@ -64,6 +64,8 @@ mypy==1.19.1
 mypy_extensions==1.1.0
 numpy==2.4.0
 oauthlib==3.3.1
+authlib==1.3.0
+itsdangerous==2.2.0
 openai==1.99.9
 packaging==25.0
 pandas==2.3.3