Add standalone form page template that bypasses the theme, with admin
setting and auto-creation on plugin activation. Fix reCAPTCHA v3 double
submission, remove jQuery dependency, extend localized JS strings, and
overhaul form CSS/JS. Update milestone audit to PASSED (9/9, 10/10, 5/5).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
