fix(ui): hide invoice list delete button for paid invoices (consistent with detail guard)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/pages/Invoices.tsx

@@ -638,7 +638,7 @@ export default function Invoices() {
               {pdfLoading === inv.id ? <CircularProgress size={16} /> : PdfIcon}
             </IconButton>
           )}
-          {hasPermission("invoices.delete") && (
+          {hasPermission("invoices.delete") && inv.status !== "paid" && (
             <IconButton
               size="small"
               color="error"