shared page: window the rendered rows — DOM no longer grows with history

The table rendered every split row (1,279 today, ~600/yr growth), so page
weight was unbounded even after the re-render fix. Render the first 100 of
the filtered/sorted set with Show more (+100) / Show all; any filter or
sort change resets the window. Data stays fully client-side on purpose —
search still counts matches across all history — only the DOM is capped.
Headless-measured expand stall: 165ms -> 35ms.

src/app/shared/page.tsx

@@ -498,6 +498,17 @@ export default function SharedPage() {
   const [paymentModal, setPaymentModal] = useState<{ id: number; name: string; balance: number } | null>(null);
   const [showHistory, setShowHistory] = useState<number | null>(null);
   const [editModal, setEditModal] = useState<SharedTransactionRow | null>(null);
+  // Rendering is windowed even though the data is not: the query returns every
+  // split row (1,279 as of 2026-08, growing ~600/yr) so search and sort stay
+  // instant over full history, but the DOM stops at visibleCount — an unbounded
+  // table was what made expanding a receipt freeze the browser. "Show more"
+  // extends the window; changing any filter resets it.
+  const [visibleCount, setVisibleCount] = useState(100);
+  useEffect(() => {
+    setVisibleCount(100);
+  }, [search, sortCol, sortDir, tagIds, participantId]);
+  const visible = (transactions as SharedTransactionRow[]).slice(0, visibleCount);
+
   // Receipt expansion, same pattern as the transactions page. The shared
   // viewer is a split participant, so /api/transactions/[id]/order
   // authorises them — the item list is part of what was shared.
@@ -681,7 +692,7 @@ export default function SharedPage() {
               </tr>
             </thead>
             <tbody>
-              {(transactions as SharedTransactionRow[]).map((tx) => (
+              {visible.map((tx) => (
                 <SharedTxRow
                   key={tx.id}
                   tx={tx}
@@ -694,6 +705,25 @@ export default function SharedPage() {
             </tbody>
           </table>
         )}
+        {!txLoading && transactions.length > visible.length && (
+          <div className="px-4 py-3 border-t border-zinc-800 flex items-center gap-3 text-xs">
+            <button
+              onClick={() => setVisibleCount((c) => c + 100)}
+              className="px-3 py-1.5 bg-zinc-800 hover:bg-zinc-700 text-zinc-300 rounded-lg"
+            >
+              Show more
+            </button>
+            <button
+              onClick={() => setVisibleCount(transactions.length)}
+              className="text-zinc-500 hover:text-zinc-300 underline underline-offset-2"
+            >
+              Show all
+            </button>
+            <span className="text-zinc-600 ml-auto tabular-nums">
+              showing {visible.length} of {transactions.length}
+            </span>
+          </div>
+        )}
       </div>
 
       {/* Payment modal */}