feat(audio): 오디오 시스템 추가

- just_audio 패키지 추가
- AudioService 구현 (BGM/SFX 재생)
- assets/audio/bgm/, assets/audio/sfx/ 에셋 추가

lib/src/core/audio/audio_service.dart

@@ -0,0 +1,228 @@
+import 'package:just_audio/just_audio.dart';
+
+import 'package:askiineverdie/src/core/storage/settings_repository.dart';
+
+/// 게임 오디오 서비스
+///
+/// BGM과 SFX를 관리하며, 설정과 연동하여 볼륨을 조절합니다.
+class AudioService {
+  AudioService({SettingsRepository? settingsRepository})
+      : _settingsRepository = settingsRepository ?? SettingsRepository();
+
+  final SettingsRepository _settingsRepository;
+
+  // BGM 플레이어
+  AudioPlayer? _bgmPlayer;
+
+  // SFX 플레이어 풀 (동시 재생 지원)
+  final List<AudioPlayer> _sfxPlayers = [];
+  static const int _maxSfxPlayers = 5;
+
+  // 현재 볼륨
+  double _bgmVolume = 0.7;
+  double _sfxVolume = 0.8;
+
+  // 현재 재생 중인 BGM
+  String? _currentBgm;
+
+  // 초기화 여부
+  bool _initialized = false;
+
+  /// 서비스 초기화
+  Future<void> init() async {
+    if (_initialized) return;
+
+    // 설정에서 볼륨 불러오기
+    _bgmVolume = await _settingsRepository.loadBgmVolume();
+    _sfxVolume = await _settingsRepository.loadSfxVolume();
+
+    // BGM 플레이어 초기화
+    _bgmPlayer = AudioPlayer();
+    await _bgmPlayer!.setLoopMode(LoopMode.one);
+    await _bgmPlayer!.setVolume(_bgmVolume);
+
+    // SFX 플레이어 풀 초기화
+    for (var i = 0; i < _maxSfxPlayers; i++) {
+      final player = AudioPlayer();
+      await player.setVolume(_sfxVolume);
+      _sfxPlayers.add(player);
+    }
+
+    _initialized = true;
+  }
+
+  /// BGM 재생
+  ///
+  /// [name]은 assets/audio/bgm/ 폴더 내 파일명 (확장자 제외)
+  /// 예: playBgm('battle') → assets/audio/bgm/battle.wav 또는 battle.mp3
+  Future<void> playBgm(String name) async {
+    if (!_initialized) await init();
+    if (_currentBgm == name) return; // 이미 재생 중
+
+    try {
+      _currentBgm = name;
+      // WAV 먼저 시도, 실패하면 MP3 시도
+      try {
+        await _bgmPlayer!.setAsset('assets/audio/bgm/$name.wav');
+      } catch (_) {
+        await _bgmPlayer!.setAsset('assets/audio/bgm/$name.mp3');
+      }
+      await _bgmPlayer!.play();
+    } catch (e) {
+      // 파일이 없으면 무시 (개발 중 에셋 미추가 상태)
+      _currentBgm = null;
+    }
+  }
+
+  /// BGM 정지
+  Future<void> stopBgm() async {
+    if (!_initialized) return;
+
+    await _bgmPlayer!.stop();
+    _currentBgm = null;
+  }
+
+  /// BGM 일시정지
+  Future<void> pauseBgm() async {
+    if (!_initialized) return;
+    await _bgmPlayer!.pause();
+  }
+
+  /// BGM 재개
+  Future<void> resumeBgm() async {
+    if (!_initialized) return;
+    if (_currentBgm != null) {
+      await _bgmPlayer!.play();
+    }
+  }
+
+  /// SFX 재생
+  ///
+  /// [name]은 assets/audio/sfx/ 폴더 내 파일명 (확장자 제외)
+  /// 예: playSfx('attack') → assets/audio/sfx/attack.wav 또는 attack.mp3
+  Future<void> playSfx(String name) async {
+    if (!_initialized) await init();
+    if (_sfxVolume == 0) return; // 볼륨이 0이면 재생 안함
+
+    // 사용 가능한 플레이어 찾기
+    AudioPlayer? availablePlayer;
+    for (final player in _sfxPlayers) {
+      if (!player.playing) {
+        availablePlayer = player;
+        break;
+      }
+    }
+
+    // 모든 플레이어가 사용 중이면 첫 번째 플레이어 재사용
+    availablePlayer ??= _sfxPlayers.first;
+
+    try {
+      // WAV 먼저 시도, 실패하면 MP3 시도
+      try {
+        await availablePlayer.setAsset('assets/audio/sfx/$name.wav');
+      } catch (_) {
+        await availablePlayer.setAsset('assets/audio/sfx/$name.mp3');
+      }
+      await availablePlayer.seek(Duration.zero);
+      await availablePlayer.play();
+    } catch (e) {
+      // 파일이 없으면 무시
+    }
+  }
+
+  /// BGM 볼륨 설정 (0.0 ~ 1.0)
+  Future<void> setBgmVolume(double volume) async {
+    _bgmVolume = volume.clamp(0.0, 1.0);
+    if (_initialized && _bgmPlayer != null) {
+      await _bgmPlayer!.setVolume(_bgmVolume);
+    }
+    await _settingsRepository.saveBgmVolume(_bgmVolume);
+  }
+
+  /// SFX 볼륨 설정 (0.0 ~ 1.0)
+  Future<void> setSfxVolume(double volume) async {
+    _sfxVolume = volume.clamp(0.0, 1.0);
+    if (_initialized) {
+      for (final player in _sfxPlayers) {
+        await player.setVolume(_sfxVolume);
+      }
+    }
+    await _settingsRepository.saveSfxVolume(_sfxVolume);
+  }
+
+  /// 현재 BGM 볼륨
+  double get bgmVolume => _bgmVolume;
+
+  /// 현재 SFX 볼륨
+  double get sfxVolume => _sfxVolume;
+
+  /// 현재 재생 중인 BGM
+  String? get currentBgm => _currentBgm;
+
+  /// 서비스 정리
+  Future<void> dispose() async {
+    await _bgmPlayer?.dispose();
+    for (final player in _sfxPlayers) {
+      await player.dispose();
+    }
+    _sfxPlayers.clear();
+    _initialized = false;
+  }
+}
+
+/// BGM 타입 열거형
+enum BgmType {
+  /// 마을/상점 BGM
+  town,
+
+  /// 일반 전투 BGM
+  battle,
+
+  /// 보스 전투 BGM
+  boss,
+
+  /// 레벨업/퀘스트 완료 팡파레
+  victory,
+}
+
+/// SFX 타입 열거형
+enum SfxType {
+  /// 공격
+  attack,
+
+  /// 피격
+  hit,
+
+  /// 스킬 사용
+  skill,
+
+  /// 아이템 획득
+  item,
+
+  /// UI 클릭
+  click,
+
+  /// 레벨업
+  levelUp,
+
+  /// 퀘스트 완료
+  questComplete,
+}
+
+/// BgmType을 파일명으로 변환
+extension BgmTypeExtension on BgmType {
+  String get fileName => name;
+}
+
+/// SfxType을 파일명으로 변환
+extension SfxTypeExtension on SfxType {
+  String get fileName => switch (this) {
+    SfxType.attack => 'attack',
+    SfxType.hit => 'hit',
+    SfxType.skill => 'skill',
+    SfxType.item => 'item',
+    SfxType.click => 'click',
+    SfxType.levelUp => 'level_up',
+    SfxType.questComplete => 'quest_complete',
+  };
+}

macos/Flutter/GeneratedPluginRegistrant.swift

@@ -5,10 +5,14 @@
 import FlutterMacOS
 import Foundation
 
+import audio_session
+import just_audio
 import path_provider_foundation
 import shared_preferences_foundation
 
 func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
+  AudioSessionPlugin.register(with: registry.registrar(forPlugin: "AudioSessionPlugin"))
+  JustAudioPlugin.register(with: registry.registrar(forPlugin: "JustAudioPlugin"))
   PathProviderPlugin.register(with: registry.registrar(forPlugin: "PathProviderPlugin"))
   SharedPreferencesPlugin.register(with: registry.registrar(forPlugin: "SharedPreferencesPlugin"))
 }

pubspec.lock

@@ -9,6 +9,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.13.0"
+  audio_session:
+    dependency: transitive
+    description:
+      name: audio_session
+      sha256: "2b7fff16a552486d078bfc09a8cde19f426dc6d6329262b684182597bec5b1ac"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.1.25"
   boolean_selector:
     dependency: transitive
     description:
@@ -41,6 +49,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.19.1"
+  crypto:
+    dependency: transitive
+    description:
+      name: crypto
+      sha256: c8ea0233063ba03258fbcf2ca4d6dadfefe14f02fab57702265467a19f27fadf
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.0.7"
   cupertino_icons:
     dependency: "direct main"
     description:
@@ -73,6 +89,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "7.0.1"
+  fixnum:
+    dependency: transitive
+    description:
+      name: fixnum
+      sha256: b6dc7065e46c974bc7c5f143080a6764ec7a4be6da1285ececdc37be96de53be
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.1.1"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -109,6 +133,30 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "0.20.2"
+  just_audio:
+    dependency: "direct main"
+    description:
+      name: just_audio
+      sha256: f978d5b4ccea08f267dae0232ec5405c1b05d3f3cd63f82097ea46c015d5c09e
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.9.46"
+  just_audio_platform_interface:
+    dependency: transitive
+    description:
+      name: just_audio_platform_interface
+      sha256: "2532c8d6702528824445921c5ff10548b518b13f808c2e34c2fd54793b999a6a"
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.6.0"
+  just_audio_web:
+    dependency: transitive
+    description:
+      name: just_audio_web
+      sha256: "6ba8a2a7e87d57d32f0f7b42856ade3d6a9fbe0f1a11fabae0a4f00bb73f0663"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.4.16"
   leak_tracker:
     dependency: transitive
     description:
@@ -237,6 +285,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.1.8"
+  rxdart:
+    dependency: transitive
+    description:
+      name: rxdart
+      sha256: "5c3004a4a8dbb94bd4bf5412a4def4acdaa12e12f269737a5751369e12d1a962"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.28.0"
   shared_preferences:
     dependency: "direct main"
     description:
@@ -330,6 +386,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.4.1"
+  synchronized:
+    dependency: transitive
+    description:
+      name: synchronized
+      sha256: c254ade258ec8282947a0acbbc90b9575b4f19673533ee46f2f6e9b3aeefd7c0
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.4.0"
   term_glyph:
     dependency: transitive
     description:
@@ -346,6 +410,22 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "0.7.6"
+  typed_data:
+    dependency: transitive
+    description:
+      name: typed_data
+      sha256: f9049c039ebfeb4cf7a7104a675823cd72dba8297f264b6637062516699fa006
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.4.0"
+  uuid:
+    dependency: transitive
+    description:
+      name: uuid
+      sha256: a11b666489b1954e01d992f3d601b1804a33937b5a8fe677bd26b8a9f96f96e8
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.5.2"
   vector_math:
     dependency: transitive
     description:

pubspec.yaml

@@ -37,6 +37,7 @@ dependencies:
   intl: ^0.20.2
   path_provider: ^2.1.4
   shared_preferences: ^2.3.1
+  just_audio: ^0.9.42
 
 dev_dependencies:
   flutter_test:
@@ -65,6 +66,8 @@ flutter:
   # To add assets to your application, add an assets section, like this:
   assets:
     - assets/
+    - assets/audio/bgm/
+    - assets/audio/sfx/
 
   # An image asset can refer to one or more resolution-specific "variants", see
   # https://flutter.dev/to/resolution-aware-images