Block warehouse placement while the city has a bane

Placing a new warehouse discards the destroyed warehouse's rubble loot,
so defenders could deny attackers the loot by rebuilding mid-siege.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/engine/net/client/handlers/PlaceAssetMsgHandler.java

@@ -532,6 +532,13 @@ public class PlaceAssetMsgHandler extends AbstractClientMsgHandler {
             return false;
         }
 
+        // A rebuilt warehouse would orphan the destroyed warehouse's loot
+
+        if (cityObject.getBane() != null) {
+            PlaceAssetMsg.sendPlaceAssetError(origin, 1, "Cannot place a warehouse during an active bane.");
+            return false;
+        }
+
         // Create the warehouse object and it's entry in the database
 
         if (createWarehouse(player, msg.getFirstPlacementInfo(), serverZone) == false) {