Add Instance Lockouts window and fix three compiler warnings

- Add Escape Menu → Instance Lockouts button opening a new panel
  that lists active lockouts with instance name (from Map.dbc),
  difficulty, time-until-reset countdown, and locked/extended status.
  map name lookup is cached on first open.
- Fix uninitialized ChatType in sendChatMessage (default to SAY)
- Remove unused startWorld variable in handleMonsterMoveTransport
- Remove unused modelCached variable in spawnOnlineCreature
  Eliminates all -Wunused-but-set-variable and -Wmaybe-uninitialized
  warnings in the main translation units.

src/core/application.cpp

@@ -4841,11 +4841,9 @@ void Application::spawnOnlineCreature(uint64_t guid, uint32_t displayId, float x
 
     // Check model cache - reuse if same displayId was already loaded
     uint32_t modelId = 0;
-    bool modelCached = false;
     auto cacheIt = displayIdModelCache_.find(displayId);
     if (cacheIt != displayIdModelCache_.end()) {
         modelId = cacheIt->second;
-        modelCached = true;
     } else {
         // Load model from disk (only once per displayId)
         modelId = nextCreatureModelId_++;