add error/loading/404 boundaries, responsive tables, Metadata API

src/components/admin/billing/generate-form.tsx

@@ -265,6 +265,7 @@ function DraftPreview({ draft }: { draft: InvoiceDraft }) {
         </div>
       )}
 
+      <div className="overflow-x-auto">
       <table className="w-full text-sm">
         <thead className="text-xs text-text-muted text-left">
           <tr>
@@ -323,6 +324,7 @@ function DraftPreview({ draft }: { draft: InvoiceDraft }) {
           )}
         </tbody>
       </table>
+      </div>
 
       <div className="mt-4 pt-3 border-t border-border space-y-1 text-sm">
         <div className="flex justify-between">