feat: support DOCX uploads via Gotenberg (#2801)

Uploaded .docx files are converted to PDF on the server using a
Gotenberg
sidecar before entering the normal envelope pipeline. The feature is
opt-in via NEXT_PRIVATE_DOCUMENT_CONVERSION_URL; when unset, only PDF
uploads are accepted.

A per-process circuit breaker opens for 30s after a conversion failure
to shed load.

Ships a dev Dockerfile that layers Microsoft Core Fonts and additional
language fonts
onto the upstream Gotenberg image for better fidelity.

Co-authored-by: Ephraim Duncan
<55143799+ephraimduncan@users.noreply.github.com>

Co-authored-by: Ephraim Duncan <55143799+ephraimduncan@users.noreply.github.com>

apps/remix/app/components/general/document/document-upload-button-legacy.tsx

@@ -140,6 +140,15 @@ export const DocumentUploadButtonLegacy = ({ className, type }: DocumentUploadBu
           'ENVELOPE_ITEM_LIMIT_EXCEEDED',
           () => msg`You have reached the limit of the number of files per envelope.`,
         )
+        .with('UNSUPPORTED_FILE_TYPE', () => msg`This file type isn't supported. Please upload a PDF or Word document.`)
+        .with(
+          'CONVERSION_SERVICE_UNAVAILABLE',
+          () => msg`Document conversion is temporarily unavailable. Please try again shortly or upload a PDF.`,
+        )
+        .with(
+          'CONVERSION_FAILED',
+          () => msg`We couldn't convert this file. Please check it's a valid Word document or upload a PDF instead.`,
+        )
         .otherwise(() => msg`An error occurred while uploading your document.`);
 
       toast({