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/direct-template/direct-template-invalid-page.tsx

@@ -0,0 +1,23 @@
+import { Trans } from '@lingui/react/macro';
+import { AlertTriangleIcon } from 'lucide-react';
+
+export const DirectTemplateInvalidPageView = () => {
+  return (
+    <div className="mx-auto flex h-[70vh] w-full max-w-md flex-col items-center justify-center">
+      <div>
+        <AlertTriangleIcon className="h-10 w-10 text-destructive" />
+
+        <h1 className="mt-4 font-semibold text-3xl">
+          <Trans>Invalid direct link template</Trans>
+        </h1>
+
+        <p className="mt-2 text-muted-foreground text-sm">
+          <Trans>
+            This direct link template cannot be used because one or more signers do not have a signature field assigned.
+            Please contact the sender to update the template.
+          </Trans>
+        </p>
+      </div>
+    </div>
+  );
+};