site-builder: relay wiring on FormContainer (template forms) + shared helper

The recipient field was only on the ContactForm block; templates build forms
from FormContainer + InputField, so template-based contact forms had no way to
set a target address. Add 'Send submissions to' + thank-you fields to
FormContainer, and extract the marker/placeholder/honeypot into a shared
form-relay-wiring helper so ContactForm and FormContainer can't drift.

craft/src/components/forms/ContactForm.tsx

@@ -1,6 +1,7 @@
 import React, { CSSProperties } from 'react';
 import { useNode, UserComponent } from '@craftjs/core';
 import { cssPropsToString } from '../../utils/style-helpers';
+import { relayFormWiring } from '../../utils/form-relay-wiring';
 
 interface ContactFormField {
   type: 'text' | 'email' | 'tel' | 'textarea' | 'select';
@@ -435,15 +436,7 @@ ContactForm.craft = {
     alignSelf: 'flex-start',
   });
 
-  const useRelay = !!props.recipientEmail;
-  const fid = 'F' + Math.random().toString(36).slice(2, 8);
-  const actionAttr = useRelay ? `__WHP_FORM_ACTION__${fid}__` : esc(props.formAction || '#');
-  const honeypot = useRelay
-    ? `<input type="text" name="_gotcha" tabindex="-1" autocomplete="off" style="position:absolute;left:-9999px" aria-hidden="true">`
-    : '';
-  const marker = useRelay
-    ? `<!--WHP-FORM id="${fid}" recipient="${esc(props.recipientEmail)}" thankyou="${esc(props.thankYouUrl || '')}"-->`
-    : '';
+  const { marker, actionAttr, honeypot } = relayFormWiring(props.recipientEmail, props.thankYouUrl, props.formAction);
 
   return {
     html: `${marker}<form action="${actionAttr}" method="POST"${formStyle ? ` style="${formStyle}"` : ''}>