(#1) - WebPack bundling of JS and CSS (#1)

This work was done with Claude.

Added bundling of CSS & JS with WebPack. This also means minimization.

---------

Co-authored-by: Martin Slachta <martin.slachta@outlook.com>
Reviewed-on: #1

assets/js/forms/RsvAdminForm.js

@@ -1,3 +1,6 @@
+import { RsvFormEncoder } from './RsvFormEncoder.js';
+import { show_notice } from '../../../src/components/admin.js';
+
 /*
  * RsvAdminForm — shared submit handler for wp-admin forms.
  *
@@ -13,7 +16,7 @@
  *     refresh:   () => my_datagrid.refresh(),
  *   });
  */
-const RsvAdminForm = {
+export const RsvAdminForm = {
   // Attach a submit listener that sends the form as JSON.
   bind(form, options = {}) {
     if (!form) return;