refactor(core): decompose Application::setupUICallbacks() into 7 domain handlers

Extract ~1,700 lines / 60+ inline [this]-capturing lambdas from the monolithic
Application::setupUICallbacks() into 7 focused callback handler classes following
the ToastManager/ChatPanel::setupCallbacks() pattern already in the codebase.

New handlers (include/core/ + src/core/):
  - NPCInteractionCallbackHandler  NPC greeting/farewell/vendor/aggro voice
  - AudioCallbackHandler           Music, positional sound, level-up, achievement, LFG
  - EntitySpawnCallbackHandler     Creature/player/GO spawn, despawn, move, state
  - AnimationCallbackHandler       Death, respawn, combat, emotes, charge, sprint, vehicle
  - TransportCallbackHandler       Mount, taxi, transport spawn/move
  - WorldEntryCallbackHandler      World entry, unstuck, hearthstone, bind point
  - UIScreenCallbackHandler        Auth, realm selection, char selection/creation/deletion

application.cpp:  4,462 → 2,791 lines  (−1,671)
setupUICallbacks: ~1,700 → ~50 lines (thin orchestrator)

Deduplication:
  resolveSoundEntryPath()   — was 3× copy-paste of SoundEntries.dbc lookup
  resolveNpcVoiceType()     — was 4× copy-paste of display-ID→voice detection
  precacheNearbyTiles()     — was 3× copy-paste of 17×17 tile loop
  4 helper lambdas          — promoted to private methods on WorldEntryCallbackHandler

State migration out of Application:
  charge* (6 vars)          → AnimationCallbackHandler
  hearth*/worldEntry*/taxi* → WorldEntryCallbackHandler
  pendingCreatedCharacterName_ → UIScreenCallbackHandler

Bug fixes:
  - Duplicate `namespace core {` in application.hpp caused wowee::std pollution
  - AppState forward decl in ui_screen_callback_handler.hpp was at wrong scope
  - world_loader.cpp accessed moved member vars directly via friend; now uses handler API

include/core/application.hpp

@@ -34,6 +34,15 @@ namespace addons { class AddonManager; }
 
 namespace core {
 
+// Handler forward declarations
+class NPCInteractionCallbackHandler;
+class AudioCallbackHandler;
+class EntitySpawnCallbackHandler;
+class AnimationCallbackHandler;
+class TransportCallbackHandler;
+class WorldEntryCallbackHandler;
+class UIScreenCallbackHandler;
+
 enum class AppState {
     AUTHENTICATION,
     REALM_SELECTION,
@@ -134,9 +143,17 @@ private:
     std::unique_ptr<WorldLoader> worldLoader_;
     std::unique_ptr<audio::AudioCoordinator> audioCoordinator_;
 
+    // Callback handlers (extracted from setupUICallbacks)
+    std::unique_ptr<NPCInteractionCallbackHandler> npcInteractionCallbacks_;
+    std::unique_ptr<AudioCallbackHandler> audioCallbacks_;
+    std::unique_ptr<EntitySpawnCallbackHandler> entitySpawnCallbacks_;
+    std::unique_ptr<AnimationCallbackHandler> animationCallbacks_;
+    std::unique_ptr<TransportCallbackHandler> transportCallbacks_;
+    std::unique_ptr<WorldEntryCallbackHandler> worldEntryCallbacks_;
+    std::unique_ptr<UIScreenCallbackHandler> uiScreenCallbacks_;
+
     AppState state = AppState::AUTHENTICATION;
     bool running = false;
-    std::string pendingCreatedCharacterName_;  // Auto-select after character creation
     bool playerCharacterSpawned = false;
     bool npcsSpawned = false;
     bool spawnSnapToGround = true;
@@ -154,27 +171,11 @@ private:
     static inline const std::string emptyString_;
     static inline const std::vector<std::string> emptyStringVec_;
 
-    bool lastTaxiFlight_ = false;
-    float taxiLandingClampTimer_ = 0.0f;
-    float worldEntryMovementGraceTimer_ = 0.0f;
-
-    // Hearth teleport: freeze player until terrain loads at destination
-    bool hearthTeleportPending_ = false;
-    glm::vec3 hearthTeleportPos_{0.0f};  // render coords
-    float hearthTeleportTimer_ = 0.0f;   // timeout safety
     float facingSendCooldown_ = 0.0f;        // Rate-limits MSG_MOVE_SET_FACING
     float lastSentCanonicalYaw_ = 1000.0f;   // Sentinel — triggers first send
     float taxiStreamCooldown_ = 0.0f;
     bool idleYawned_ = false;
 
-    // Charge rush state
-    bool chargeActive_ = false;
-    float chargeTimer_ = 0.0f;
-    float chargeDuration_ = 0.0f;
-    glm::vec3 chargeStartPos_{0.0f};  // Render coordinates
-    glm::vec3 chargeEndPos_{0.0f};    // Render coordinates
-    uint64_t chargeTargetGuid_ = 0;
-
     bool wasAutoAttacking_ = false;
 
     // Quest marker billboard sprites (above NPCs)