Add Google reCAPTCHA v2 to Legacy QuoteForms

Add Google reCAPTCHA v2 verification to the Legacy Quote Form flow. Before a visitor can advance past the Personal Details step, they will be required to complete a reCAPTCHA challenge. This protects the form from automated submissions and bots. The feature will be controlled by a per-form toggle in the Form Builder, defaulting to off so existing forms are unaffected.