feat: show zone entry text on every zone crossing via SMSG_INIT_WORLD_STATES

Previously the "Entering: [Zone]" overlay only triggered when the terrain
renderer loaded a new map. Now it also fires whenever worldStateZoneId_
changes (sent by the server via SMSG_INIT_WORLD_STATES on each zone
crossing), giving correct "Entering: Ironforge", "Entering: Wailing
Caverns" etc. display for sub-zones and dungeon entries without requiring
a full map reload.

- Added lastKnownWorldStateZoneId_ to track server-reported zone changes
- renderZoneText() now takes GameHandler& to access getWorldStateZoneId()
  and getWhoAreaName() for name lookup via WorldMapArea.dbc cache
- Renderer zone name still checked as a fallback for map-level transitions
- Both sources de-duplicate to avoid triggering the same text twice

include/ui/game_screen.hpp

@@ -634,7 +634,8 @@ private:
     float zoneTextTimer_ = 0.0f;
     std::string zoneTextName_;
     std::string lastKnownZoneName_;
-    void renderZoneText();
+    uint32_t lastKnownWorldStateZoneId_ = 0;
+    void renderZoneText(game::GameHandler& gameHandler);
     void renderWeatherOverlay(game::GameHandler& gameHandler);
 
     // Cooldown tracker