feat: validate signers have signature fields before distribution (#2411)

API users were inadvertently sending documents without signature fields,
causing confusion for recipients and breaking their signing flows.

- Add getRecipientsWithMissingFields helper in recipients.ts
- Add server-side validation in sendDocument to block distribution
- Fix v1 API to return 400 instead of 500 for validation errors
- Consolidate UI signature field checks to use isSignatureFieldType
- Add E2E tests for both v1 and v2 APIs

apps/remix/app/components/dialogs/envelope-distribute-dialog.tsx

@@ -3,13 +3,7 @@ import { useEffect, useMemo, useState } from 'react';
 import { zodResolver } from '@hookform/resolvers/zod';
 import { useLingui } from '@lingui/react/macro';
 import { Trans } from '@lingui/react/macro';
-import {
-  DocumentDistributionMethod,
-  DocumentStatus,
-  EnvelopeType,
-  FieldType,
-  RecipientRole,
-} from '@prisma/client';
+import { DocumentDistributionMethod, DocumentStatus, EnvelopeType } from '@prisma/client';
 import { AnimatePresence, motion } from 'framer-motion';
 import { InfoIcon } from 'lucide-react';
 import { useForm } from 'react-hook-form';
@@ -20,6 +14,7 @@ import * as z from 'zod';
 import { useCurrentEnvelopeEditor } from '@documenso/lib/client-only/providers/envelope-editor-provider';
 import { useCurrentOrganisation } from '@documenso/lib/client-only/providers/organisation';
 import { extractDocumentAuthMethods } from '@documenso/lib/utils/document-auth';
+import { getRecipientsWithMissingFields } from '@documenso/lib/utils/recipients';
 import { trpc, trpc as trpcReact } from '@documenso/trpc/react';
 import { DocumentSendEmailMessageHelper } from '@documenso/ui/components/document/document-send-email-message-helper';
 import { cn } from '@documenso/ui/lib/utils';
@@ -140,14 +135,7 @@ export const EnvelopeDistributeDialog = ({
   );
 
   const recipientsMissingSignatureFields = useMemo(
-    () =>
-      recipientsWithIndex.filter(
-        (recipient) =>
-          recipient.role === RecipientRole.SIGNER &&
-          !envelope.fields.some(
-            (field) => field.type === FieldType.SIGNATURE && field.recipientId === recipient.id,
-          ),
-      ),
+    () => getRecipientsWithMissingFields(recipientsWithIndex, envelope.fields),
     [recipientsWithIndex, envelope.fields],
   );