refactor: decouple Application singleton by extracting core subsystems and updating interfaces

- Add `audio::AudioCoordinator` interface and implementation
- Modify `Application` to reduce singleton usage and move controller responsibilities:
  - application.hpp
  - application.cpp
- Update UI and audio headers/sources:
  - game_screen.hpp
  - game_screen.cpp
  - ui_manager.hpp
  - audio_coordinator.hpp
  - audio_coordinator.cpp
- Project config touched:
  - CMakeLists.txt

src/audio/audio_coordinator.cpp

@@ -0,0 +1,87 @@
+#include "audio/audio_coordinator.hpp"
+#include "audio/audio_engine.hpp"
+#include "audio/music_manager.hpp"
+#include "audio/footstep_manager.hpp"
+#include "audio/activity_sound_manager.hpp"
+#include "audio/mount_sound_manager.hpp"
+#include "audio/npc_voice_manager.hpp"
+#include "audio/ambient_sound_manager.hpp"
+#include "audio/ui_sound_manager.hpp"
+#include "audio/combat_sound_manager.hpp"
+#include "audio/spell_sound_manager.hpp"
+#include "audio/movement_sound_manager.hpp"
+#include "pipeline/asset_manager.hpp"
+#include "core/logger.hpp"
+
+namespace wowee {
+namespace audio {
+
+AudioCoordinator::AudioCoordinator() = default;
+
+AudioCoordinator::~AudioCoordinator() {
+    shutdown();
+}
+
+bool AudioCoordinator::initialize() {
+    // Initialize AudioEngine (singleton)
+    if (!AudioEngine::instance().initialize()) {
+        LOG_WARNING("Failed to initialize AudioEngine - audio will be disabled");
+        audioAvailable_ = false;
+        return false;
+    }
+    audioAvailable_ = true;
+
+    // Create all audio managers (initialized later with asset manager)
+    musicManager_ = std::make_unique<MusicManager>();
+    footstepManager_ = std::make_unique<FootstepManager>();
+    activitySoundManager_ = std::make_unique<ActivitySoundManager>();
+    mountSoundManager_ = std::make_unique<MountSoundManager>();
+    npcVoiceManager_ = std::make_unique<NpcVoiceManager>();
+    ambientSoundManager_ = std::make_unique<AmbientSoundManager>();
+    uiSoundManager_ = std::make_unique<UiSoundManager>();
+    combatSoundManager_ = std::make_unique<CombatSoundManager>();
+    spellSoundManager_ = std::make_unique<SpellSoundManager>();
+    movementSoundManager_ = std::make_unique<MovementSoundManager>();
+
+    LOG_INFO("AudioCoordinator initialized with ", 10, " audio managers");
+    return true;
+}
+
+void AudioCoordinator::initializeWithAssets(pipeline::AssetManager* assetManager) {
+    if (!audioAvailable_ || !assetManager) return;
+
+    // MusicManager needs asset manager for zone music lookups
+    if (musicManager_) {
+        musicManager_->initialize(assetManager);
+    }
+
+    // Other managers may need asset manager for sound bank loading
+    // (Add similar calls as needed for other managers)
+
+    LOG_INFO("AudioCoordinator initialized with asset manager");
+}
+
+void AudioCoordinator::shutdown() {
+    // Reset all managers first (they may reference AudioEngine)
+    movementSoundManager_.reset();
+    spellSoundManager_.reset();
+    combatSoundManager_.reset();
+    uiSoundManager_.reset();
+    ambientSoundManager_.reset();
+    npcVoiceManager_.reset();
+    mountSoundManager_.reset();
+    activitySoundManager_.reset();
+    footstepManager_.reset();
+    musicManager_.reset();
+
+    // Shutdown audio engine last
+    if (audioAvailable_) {
+        AudioEngine::instance().shutdown();
+        audioAvailable_ = false;
+    }
+
+    LOG_INFO("AudioCoordinator shutdown complete");
+}
+
+} // namespace audio
+} // namespace wowee