fix: sidebar nav highlights both Trading Controls and Trading Engine

When on /trading/engine, the /trading nav item also matched via
startsWith. Now checks if a more specific child route matches
first and uses exact match in that case.

frontend/src/components/AppLayout.tsx

@@ -70,10 +70,16 @@ export function AppLayout({ children }: { children: ReactNode }) {
           {navItems.map((item) => {
             const showGroup = item.group && item.group !== lastGroup;
             lastGroup = item.group;
+            // Check if another nav item is a more specific match (child route)
+            const hasMoreSpecificMatch = navItems.some(
+              (other) => other.to !== item.to && other.to.startsWith(item.to + '/') && currentPath.startsWith(other.to),
+            );
             const active =
               item.to === '/'
                 ? currentPath === '/'
-                : currentPath.startsWith(item.to);
+                : hasMoreSpecificMatch
+                  ? currentPath === item.to
+                  : currentPath === item.to || currentPath.startsWith(item.to + '/');
 
             return (
               <div key={item.to}>