CRITICAL FIX: Newsletter subscription was returning "Forbidden" error
because the CSRF protection was incorrectly configured.
Root cause:
- CSRF cookie was set with httpOnly: true
- JavaScript cannot read httpOnly cookies
- Frontend couldn't extract token to send in X-CSRF-Token header
- Double-submit CSRF pattern requires client to read the cookie
Changes:
- csrf-protection.middleware.js: Set httpOnly: false (required for double-submit pattern)
- blog.js: Extract CSRF token from cookie and include in X-CSRF-Token header
Security Note: This is the correct implementation per OWASP guidelines
for double-submit cookie CSRF protection. The cookie is still protected
by SameSite: strict and domain restrictions.
Fixes: #newsletter-subscription-forbidden-mobile
cfc4347e9b