Wire ambient sound zone detection: setZoneType/setCityType was never called

Add AmbientSoundManager::setZoneId() that maps WoW zone IDs to the
appropriate ZoneType (forest/grasslands/desert/jungle/marsh/beach) or
CityType (Stormwind/Ironforge/Darnassus/Orgrimmar/Undercity/ThunderBluff)
and delegates to setZoneType/setCityType. Call it from the renderer's
zone transition handler so zone ambience (looping sounds, city bells,
etc.) actually activates when the player enters a zone.

include/audio/ambient_sound_manager.hpp

@@ -45,6 +45,9 @@ public:
     void setZoneType(ZoneType type);
     ZoneType getCurrentZone() const { return currentZone_; }
 
+    // Convenience: derive ZoneType and CityType from a WoW zone ID
+    void setZoneId(uint32_t zoneId);
+
     // City ambience control
     enum class CityType {
         NONE,