fix: render error messages for invalid templates (#3088)

Currently direct templates can be created without the required
signatures fields for signers.

This means that the document can be fully signed by everyone but will
ultimately fail the sealing step which leaves the document in an
unrecoverable state.

apps/remix/app/components/general/envelope-editor/envelope-editor-preview-page.tsx

@@ -22,6 +22,7 @@ import { match } from 'ts-pattern';
 import { EnvelopeGenericPageRenderer } from '~/components/general/envelope-editor/envelope-generic-page-renderer';
 import { EnvelopePdfViewer } from '~/components/general/pdf-viewer/envelope-pdf-viewer';
 
+import { EnvelopeEditorInvalidDirectTemplateAlert } from './envelope-editor-invalid-direct-template-alert';
 import { EnvelopeRendererFileSelector } from './envelope-file-selector';
 
 export const EnvelopeEditorPreviewPage = () => {
@@ -228,6 +229,8 @@ export const EnvelopeEditorPreviewPage = () => {
           {/* Horizontal envelope item selector */}
           <EnvelopeRendererFileSelector className="px-0" fields={editorFields.localFields} />
 
+          <EnvelopeEditorInvalidDirectTemplateAlert className="mb-4" />
+
           <Alert variant="warning" className="mx-auto max-w-[800px]">
             <AlertTitle>
               <Trans>Preview Mode</Trans>