Fix mobile back navigation losing overlay state on classification page

web/src/hooks/use-history-back.ts

@@ -34,7 +34,12 @@ export function useHistoryBack({
         // Store the current URL (pathname + search, without hash) before pushing history state
         urlWhenOpenedRef.current =
           window.location.pathname + window.location.search;
-        window.history.pushState({ overlayOpen: true }, "");
+        // Preserve existing history state (including React Router state) so that
+        // navigating back to this entry doesn't lose location.state values
+        window.history.pushState(
+          { ...window.history.state, overlayOpen: true },
+          "",
+        );
         historyPushedRef.current = true;
       }
 
@@ -71,4 +76,15 @@ export function useHistoryBack({
       urlWhenOpenedRef.current = null;
     }
   }, [enabled, open]);
+
+  // Clean up stale history entry if the component unmounts while the overlay
+  // is still open (e.g. parent component removed from the tree)
+  React.useEffect(() => {
+    return () => {
+      if (historyPushedRef.current) {
+        historyPushedRef.current = false;
+        window.history.back();
+      }
+    };
+  }, []);
 }