Implement Google Captcha on registration to prevent abuse

[AnantaPodder]

Integrate Google Captcha into the registration process to mitigate automated and malicious sign-ups. This will help protect the LinkLens application from spam and abuse during user registration.

Requirements:

• Integrate Google Captcha (v2 or v3) on the registration page
• Update the front-end to display and validate the captcha
• Update the back-end to verify the captcha token before allowing registration
• Ensure proper error handling and user feedback for failed captcha verifications
• Test the end-to-end registration flow with captcha enabled

This feature will enhance the security and integrity of the registration process.