feat: allow recipients to view completed PDF via QR share link

Add allowPublicCompletedDocumentAccess toggle at org/team level
(team inherits from org via null). Recipients see a "View completed
PDF" button on the signing completion page that links to /share/qr_*.

- DB migration adding toggle to OrganisationGlobalSettings and TeamGlobalSettings
- Settings UI for org and team document preferences
- Rate limiting on QR share view and file download endpoints
- Structured error responses with support codes in share route ErrorBoundary
- Exponential backoff retry when qrToken not yet available post-completion
- QR-authenticated viewers restricted to signed PDF only (no original)
- E2E tests covering happy path, not-yet-completed, invalid token, and toggle revocation

apps/remix/app/components/general/envelope-editor/envelope-file-selector.tsx

@@ -61,6 +61,10 @@ export const EnvelopeRendererFileSelector = ({
 }: EnvelopeRendererFileSelectorProps) => {
   const { envelopeItems, currentEnvelopeItem, setCurrentEnvelopeItem } = useCurrentEnvelopeRender();
 
+  if (envelopeItems.length <= 1) {
+    return null;
+  }
+
   return (
     <div className={cn('flex h-fit flex-shrink-0 space-x-2 overflow-x-auto p-4', className)}>
       {envelopeItems.map((doc, i) => (