fix: improve error handling in admin trades fetch functions

- Return errors from fetch functions instead of setting state directly
- Clear error state before starting a new fetch
- Combine errors when both upcoming and past trades fail to load
- Handle fetch errors in handleAction as well

frontend/app/admin/trades/page.tsx

@@ -45,17 +45,18 @@ export default function AdminTradesPage() {
   const [statusFilter, setStatusFilter] = useState<string>("all");
   const [userSearch, setUserSearch] = useState("");
 
-  const fetchUpcomingTrades = useCallback(async () => {
+  const fetchUpcomingTrades = useCallback(async (): Promise<string | null> => {
     try {
       const data = await api.get<AdminExchangeResponse[]>("/api/admin/trades/upcoming");
       setUpcomingTrades(data);
+      return null;
     } catch (err) {
       console.error("Failed to fetch upcoming trades:", err);
-      setError("Failed to load upcoming trades");
+      return "Failed to load upcoming trades";
     }
   }, []);
 
-  const fetchPastTrades = useCallback(async () => {
+  const fetchPastTrades = useCallback(async (): Promise<string | null> => {
     try {
       let url = "/api/admin/trades/past";
       const params = new URLSearchParams();
@@ -73,18 +74,28 @@ export default function AdminTradesPage() {
 
       const data = await api.get<AdminExchangeResponse[]>(url);
       setPastTrades(data);
+      return null;
     } catch (err) {
       console.error("Failed to fetch past trades:", err);
-      setError("Failed to load past trades");
+      return "Failed to load past trades";
     }
   }, [statusFilter, userSearch]);
 
   useEffect(() => {
     if (user && isAuthorized) {
       setIsLoadingTrades(true);
-      Promise.all([fetchUpcomingTrades(), fetchPastTrades()]).finally(() => {
-        setIsLoadingTrades(false);
-      });
+      setError(null);
+      Promise.all([fetchUpcomingTrades(), fetchPastTrades()])
+        .then(([upcomingErr, pastErr]) => {
+          // Combine errors if both failed
+          const errors = [upcomingErr, pastErr].filter(Boolean);
+          if (errors.length > 0) {
+            setError(errors.join("; "));
+          }
+        })
+        .finally(() => {
+          setIsLoadingTrades(false);
+        });
     }
   }, [user, isAuthorized, fetchUpcomingTrades, fetchPastTrades]);
 
@@ -99,7 +110,12 @@ export default function AdminTradesPage() {
           : `/api/admin/trades/${tradeId}/${action}`;
 
       await api.post<AdminExchangeResponse>(endpoint, {});
-      await Promise.all([fetchUpcomingTrades(), fetchPastTrades()]);
+      // Refetch trades - errors from fetch are informational, not critical
+      const [upcomingErr, pastErr] = await Promise.all([fetchUpcomingTrades(), fetchPastTrades()]);
+      const fetchErrors = [upcomingErr, pastErr].filter(Boolean);
+      if (fetchErrors.length > 0) {
+        setError(fetchErrors.join("; "));
+      }
       setConfirmAction(null);
     } catch (err) {
       setError(err instanceof Error ? err.message : `Failed to ${action} trade`);