fix: use Set for actioningIds to prevent race condition

Replace single actioningId state with a Set of IDs to properly
track multiple concurrent actions. This prevents issues when
a user rapidly clicks actions on different trades before the
previous action completes.

frontend/app/admin/trades/page.tsx

@@ -34,8 +34,8 @@ export default function AdminTradesPage() {
   const [isLoadingTrades, setIsLoadingTrades] = useState(true);
   const [error, setError] = useState<string | null>(null);
 
-  // Action state
-  const [actioningId, setActioningId] = useState<number | null>(null);
+  // Action state - use Set to track multiple concurrent actions
+  const [actioningIds, setActioningIds] = useState<Set<number>>(new Set());
   const [confirmAction, setConfirmAction] = useState<{
     id: number;
     type: "complete" | "no_show" | "cancel";
@@ -100,7 +100,8 @@ export default function AdminTradesPage() {
   }, [user, isAuthorized, fetchUpcomingTrades, fetchPastTrades]);
 
   const handleAction = async (tradeId: number, action: "complete" | "no_show" | "cancel") => {
-    setActioningId(tradeId);
+    // Add this trade to the set of actioning trades
+    setActioningIds((prev) => new Set(prev).add(tradeId));
     setError(null);
 
     try {
@@ -120,7 +121,12 @@ export default function AdminTradesPage() {
     } catch (err) {
       setError(err instanceof Error ? err.message : `Failed to ${action} trade`);
     } finally {
-      setActioningId(null);
+      // Remove this trade from the set of actioning trades
+      setActioningIds((prev) => {
+        const next = new Set(prev);
+        next.delete(tradeId);
+        return next;
+      });
     }
   };
 
@@ -284,14 +290,14 @@ export default function AdminTradesPage() {
                         <>
                           <button
                             onClick={() => handleAction(trade.id, confirmAction.type)}
-                            disabled={actioningId === trade.id}
+                            disabled={actioningIds.has(trade.id)}
                             style={
                               confirmAction.type === "cancel"
                                 ? styles.dangerButton
                                 : styles.successButton
                             }
                           >
-                            {actioningId === trade.id ? "..." : "Confirm"}
+                            {actioningIds.has(trade.id) ? "..." : "Confirm"}
                           </button>
                           <button
                             onClick={() => setConfirmAction(null)}