fix: clear lastInteractedGoGuid_ on world transfer in handleNewWorld

Same-map teleports (dungeon teleporters, etc.) clear casting state but
were not clearing lastInteractedGoGuid_.  If a gather cast was in progress
when the teleport happened, the stale GO guid could theoretically trigger
a spurious CMSG_LOOT on the destination map.

Also clears lastInteractedGoGuid_ in handleNewWorld alongside the rest of
the casting-state teardown for consistency with other reset paths.

src/game/game_handler.cpp

@@ -19533,6 +19533,7 @@ void GameHandler::handleNewWorld(network::Packet& packet) {
     castIsChannel = false;
     currentCastSpellId = 0;
     pendingGameObjectInteractGuid_ = 0;
+    lastInteractedGoGuid_ = 0;
     castTimeRemaining = 0.0f;
 
     // Send MSG_MOVE_WORLDPORT_ACK to tell the server we're ready