feat(12.1-01): cabana.ForbiddenError answers a refused write with 403

- hooks and bulk, record, toolbar and widget actions may return it
- 403 forbidden with the localized message and field details; the write's
  transaction is rolled back; other errors stay the opaque 500
- form shows a refused save as a persistent banner and keeps the values;
  a refused delete is a toast
- smoke tests, OpenAPI notes, dist, README, docs

modules/boardwalk/dist/index.html

@@ -6,7 +6,7 @@
     <meta name="robots" content="noindex, nofollow" />
     <meta name="summer-admin-base" content="__SUMMER_ADMIN_BASE__" />
     <title>SummerCMS</title>
-    <script type="module" crossorigin src="./assets/index-BgVbexs3.js"></script>
+    <script type="module" crossorigin src="./assets/index-8CEYdgqp.js"></script>
     <link rel="stylesheet" crossorigin href="./assets/index-BxJxH4xB.css">
   </head>
   <body>