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

src/core/audio_callback_handler.cpp

@@ -0,0 +1,132 @@
+#include "core/audio_callback_handler.hpp"
+#include "core/coordinates.hpp"
+#include "core/logger.hpp"
+#include "rendering/renderer.hpp"
+#include "pipeline/dbc_loader.hpp"
+#include "game/game_handler.hpp"
+#include "audio/audio_coordinator.hpp"
+#include "audio/music_manager.hpp"
+#include "audio/audio_engine.hpp"
+#include "ui/ui_manager.hpp"
+
+namespace wowee { namespace core {
+
+AudioCallbackHandler::AudioCallbackHandler(
+    pipeline::AssetManager& assetManager,
+    audio::AudioCoordinator* audioCoordinator,
+    rendering::Renderer* renderer,
+    ui::UIManager* uiManager,
+    game::GameHandler& gameHandler)
+    : assetManager_(assetManager)
+    , audioCoordinator_(audioCoordinator)
+    , renderer_(renderer)
+    , uiManager_(uiManager)
+    , gameHandler_(gameHandler)
+{
+}
+
+std::optional<std::string> AudioCallbackHandler::resolveSoundEntryPath(uint32_t soundId) const {
+    auto dbc = assetManager_.loadDBC("SoundEntries.dbc");
+    if (!dbc || !dbc->isLoaded()) return std::nullopt;
+
+    int32_t idx = dbc->findRecordById(soundId);
+    if (idx < 0) return std::nullopt;
+
+    // SoundEntries.dbc (WotLK): field 2 = Name (label), fields 3-12 = File[0..9], field 23 = DirectoryBase
+    const uint32_t row = static_cast<uint32_t>(idx);
+    std::string dir = dbc->getString(row, 23);
+    for (uint32_t f = 3; f <= 12; ++f) {
+        std::string name = dbc->getString(row, f);
+        if (name.empty()) continue;
+        return dir.empty() ? name : dir + "\\" + name;
+    }
+    return std::nullopt;
+}
+
+void AudioCallbackHandler::setupCallbacks() {
+    // Level-up callback — play sound, cheer emote, and trigger UI ding overlay + 3D effect
+    gameHandler_.setLevelUpCallback([this](uint32_t newLevel) {
+        if (uiManager_) {
+            uiManager_->getGameScreen().toastManager().triggerDing(newLevel);
+        }
+        if (renderer_) {
+            renderer_->triggerLevelUpEffect(renderer_->getCharacterPosition());
+        }
+    });
+
+    // Achievement earned callback — show toast banner
+    gameHandler_.setAchievementEarnedCallback([this](uint32_t achievementId, const std::string& name) {
+        if (uiManager_) {
+            uiManager_->getGameScreen().toastManager().triggerAchievementToast(achievementId, name);
+        }
+    });
+
+    // Server-triggered music callback (SMSG_PLAY_MUSIC)
+    // Resolves soundId → SoundEntries.dbc → MPQ path → MusicManager.
+    gameHandler_.setPlayMusicCallback([this](uint32_t soundId) {
+        if (!renderer_) return;
+        auto* music = audioCoordinator_ ? audioCoordinator_->getMusicManager() : nullptr;
+        if (!music) return;
+
+        auto path = resolveSoundEntryPath(soundId);
+        if (path) {
+            music->playMusic(*path, /*loop=*/false);
+        }
+    });
+
+    // SMSG_PLAY_SOUND: look up SoundEntries.dbc and play 2-D sound effect
+    gameHandler_.setPlaySoundCallback([this](uint32_t soundId) {
+        auto path = resolveSoundEntryPath(soundId);
+        if (path) {
+            audio::AudioEngine::instance().playSound2D(*path);
+        }
+    });
+
+    // SMSG_PLAY_OBJECT_SOUND / SMSG_PLAY_SPELL_IMPACT: play as 3D positional sound at source entity
+    gameHandler_.setPlayPositionalSoundCallback([this](uint32_t soundId, uint64_t sourceGuid) {
+        auto path = resolveSoundEntryPath(soundId);
+        if (!path) return;
+
+        // Play as 3D sound if source entity position is available.
+        // Entity stores canonical coords; listener uses render coords (camera).
+        auto entity = gameHandler_.getEntityManager().getEntity(sourceGuid);
+        if (entity) {
+            glm::vec3 canonical{entity->getLatestX(), entity->getLatestY(), entity->getLatestZ()};
+            glm::vec3 pos = core::coords::canonicalToRender(canonical);
+            audio::AudioEngine::instance().playSound3D(*path, pos);
+        } else {
+            audio::AudioEngine::instance().playSound2D(*path);
+        }
+    });
+
+    // Other player level-up callback — trigger 3D effect + chat notification
+    gameHandler_.setOtherPlayerLevelUpCallback([this](uint64_t guid, uint32_t newLevel) {
+        if (!renderer_) return;
+
+        // Trigger 3D effect at the other player's position
+        auto entity = gameHandler_.getEntityManager().getEntity(guid);
+        if (entity) {
+            glm::vec3 canonical(entity->getX(), entity->getY(), entity->getZ());
+            glm::vec3 renderPos = core::coords::canonicalToRender(canonical);
+            renderer_->triggerLevelUpEffect(renderPos);
+        }
+
+        // Show chat message if in group
+        if (gameHandler_.isInGroup()) {
+            std::string name = gameHandler_.getCachedPlayerName(guid);
+            if (name.empty()) name = "A party member";
+            game::MessageChatData msg;
+            msg.type = game::ChatType::SYSTEM;
+            msg.language = game::ChatLanguage::UNIVERSAL;
+            msg.message = name + " has reached level " + std::to_string(newLevel) + "!";
+            gameHandler_.addLocalChatMessage(msg);
+        }
+    });
+
+    // Open dungeon finder callback — server sends SMSG_OPEN_LFG_DUNGEON_FINDER
+    gameHandler_.setOpenLfgCallback([this]() {
+        if (uiManager_) uiManager_->getGameScreen().openDungeonFinder();
+    });
+}
+
+}} // namespace wowee::core