feat(uat-batch-14): InterestDocumentsTab rename, custom-field tooltip, yacht Transfer surface

- InterestDocumentsTab section "Legal documents" renamed to
  "Signature documents" so its scope is unambiguous. The section
  holds Documenso envelopes (EOI / Reservation / Contract); generic
  legal uploads belong in Attachments below.
- Custom-field admin form's "Sort Order" label now uses the
  FieldLabel primitive with an explainer tooltip ("Lower numbers
  render first... use to pin frequently-edited fields to the top").
  First adoption of the FieldLabel primitive shipped in PR4.2.
- Yacht Ownership History tab gains a "Transfer ownership" button:
  in the populated state as a header CTA (perm-gated by yachts.edit),
  in the empty state as the EmptyState action. Reuses the existing
  YachtTransferDialog from the header. Closes the "no way to enter/
  change" UX gap without duplicating the transfer logic.
- Verified the existing row-owner rendering already uses OwnerLink,
  so the row-click affordance was already in place.

tsc clean. 1419/1419 vitest pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/interests/interest-documents-tab.tsx

@@ -97,7 +97,7 @@ export function InterestDocumentsTab({ interestId }: InterestDocumentsTabProps)
     <div className="space-y-8">
       <section className="space-y-4">
         <div className="flex items-center justify-between">
-          <h3 className="text-sm font-medium text-muted-foreground">Legal documents</h3>
+          <h3 className="text-sm font-medium text-muted-foreground">Signature documents</h3>
           <Button size="sm" variant="outline" onClick={() => setEoiDialogOpen(true)}>
             Generate EOI
           </Button>