- Add Access-Control-Expose-Headers to allow frontend to read X-CSRF-Token response header
- Implement proactive CSRF token issuance on GET requests when session exists but CSRF cookie is missing
- Ensures frontend always has valid CSRF token before making POST requests
- Fixes 403 Forbidden errors when toggling system settings
This resolves CSRF validation failures that occurred when CSRF tokens expired or were missing while valid sessions existed.
