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-upload-page.tsx

@@ -26,6 +26,7 @@ import { ErrorCode as DropzoneErrorCode, type FileRejection, useDropzone } from
 
 import { EnvelopeItemDeleteDialog } from '~/components/dialogs/envelope-item-delete-dialog';
 
+import { EnvelopeEditorInvalidDirectTemplateAlert } from './envelope-editor-invalid-direct-template-alert';
 import { EnvelopeEditorRecipientForm } from './envelope-editor-recipient-form';
 import { EnvelopeItemTitleInput } from './envelope-editor-title-input';
 
@@ -449,6 +450,9 @@ export const EnvelopeEditorUploadPage = () => {
   return (
     <div className="mx-auto max-w-4xl space-y-6 p-8">
       <input {...getReplaceInputProps()} />
+
+      <EnvelopeEditorInvalidDirectTemplateAlert className="max-w-none" />
+
       <Card backdropBlur={false} className="border">
         <CardHeader className="pb-3">
           <CardTitle>