feat(security): add Cloudflare Turnstile CAPTCHA to registration form

- Add Turnstile widget rendering in RegisterPage on step 2
- Implement programmatic widget initialization with callbacks
- Add token validation before form submission
- Update AuthContext and API service to pass turnstileToken
- Add backend verification via Cloudflare API in register controller
- Include client IP in verification request
- Add validation rule for turnstileToken
- Reset widget on registration error

backend/src/routes/public.js

@@ -79,8 +79,6 @@ router.post('/contact', [
     const turnstileSecret = process.env.TURNSTILE_SECRET_KEY;
     const turnstileVerifyUrl = 'https://challenges.cloudflare.com/turnstile/v0/siteverify';
 
-    console.log('[Turnstile] Verifying token, secret present:', !!turnstileSecret);
-
     try {
       const turnstileResponse = await fetch(turnstileVerifyUrl, {
         method: 'POST',
@@ -93,7 +91,6 @@ router.post('/contact', [
       });
 
       const turnstileResult = await turnstileResponse.json();
-      console.log('[Turnstile] Verification result:', JSON.stringify(turnstileResult));
 
       if (!turnstileResult.success) {
         return res.status(400).json({