Collect first/last name on the mailing-list subscribe form

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

layouts/submissions/list.html

@@ -70,6 +70,12 @@
 <p style="margin-top:2rem;">We're not currently accepting submissions, but you can join our mailing list to hear when that changes.</p>
 
 <form id="subscribe-form" style="margin-top:1.5rem;">
+  <label for="subscribe-first-name">First name</label>
+  <input type="text" id="subscribe-first-name" name="first_name" required autocomplete="given-name">
+
+  <label for="subscribe-last-name">Last name (optional)</label>
+  <input type="text" id="subscribe-last-name" name="last_name" autocomplete="family-name">
+
   <label for="email">Email</label>
   <input type="email" id="email" name="email" required autocomplete="email">
 
@@ -90,6 +96,8 @@
       e.preventDefault();
       var payload = {
         email: form.email.value,
+        first_name: form.first_name.value,
+        last_name: form.last_name.value,
         website: form.website.value
       };
       var submitBtn = form.querySelector("button[type=submit]");