feat(l10n): 국제화(L10n) 시스템 도입 및 하드코딩 텍스트 변환

- flutter_localizations 및 intl 패키지 추가
- l10n.yaml 설정 파일 및 app_ko.arb 메시지 파일 생성
- 모든 화면(app, front, game_play, new_character, save_picker)의 하드코딩 텍스트를 L10n 키로 변환
- 테스트 파일에 localizationsDelegates 추가하여 L10n 지원

lib/l10n/app_ko.arb

@@ -0,0 +1,75 @@
+{
+  "@@locale": "ko",
+
+  "appTitle": "Ascii Never Die",
+  "tagNoNetwork": "No network",
+  "tagIdleRpg": "Idle RPG loop",
+  "tagLocalSaves": "Local saves",
+  "newCharacter": "New character",
+  "loadSave": "Load save",
+  "loadGame": "Load Game",
+  "viewBuildPlan": "View build plan",
+  "buildRoadmap": "Build roadmap",
+  "techStack": "Tech stack",
+  "cancel": "Cancel",
+  "exitGame": "Exit Game",
+  "saveProgressQuestion": "Save your progress before leaving?",
+  "exitWithoutSaving": "Exit without saving",
+  "saveAndExit": "Save and Exit",
+  "progressQuestTitle": "Progress Quest - {name}",
+  "levelUp": "Level Up",
+  "completeQuest": "Complete Quest",
+  "completePlot": "Complete Plot",
+  "characterSheet": "Character Sheet",
+  "traits": "Traits",
+  "stats": "Stats",
+  "experience": "Experience",
+  "xpNeededForNextLevel": "XP needed for next level",
+  "spellBook": "Spell Book",
+  "noSpellsYet": "No spells yet",
+  "equipment": "Equipment",
+  "inventory": "Inventory",
+  "encumbrance": "Encumbrance",
+  "plotDevelopment": "Plot Development",
+  "quests": "Quests",
+  "traitName": "Name",
+  "traitRace": "Race",
+  "traitClass": "Class",
+  "traitLevel": "Level",
+  "statStr": "STR",
+  "statCon": "CON",
+  "statDex": "DEX",
+  "statInt": "INT",
+  "statWis": "WIS",
+  "statCha": "CHA",
+  "statHpMax": "HP Max",
+  "statMpMax": "MP Max",
+  "equipWeapon": "Weapon",
+  "equipShield": "Shield",
+  "equipHelm": "Helm",
+  "equipHauberk": "Hauberk",
+  "equipBrassairts": "Brassairts",
+  "equipVambraces": "Vambraces",
+  "equipGauntlets": "Gauntlets",
+  "equipGambeson": "Gambeson",
+  "equipCuisses": "Cuisses",
+  "equipGreaves": "Greaves",
+  "equipSollerets": "Sollerets",
+  "gold": "Gold",
+  "goldAmount": "Gold: {amount}",
+  "prologue": "Prologue",
+  "actNumber": "Act {number}",
+  "noActiveQuests": "No active quests",
+  "questNumber": "Quest #{number}",
+  "welcomeMessage": "Welcome to Progress Quest!",
+  "noSavedGames": "No saved games found.",
+  "loadError": "Failed to load save file: {error}",
+  "name": "Name",
+  "generateName": "Generate Name",
+  "total": "Total",
+  "unroll": "Unroll",
+  "roll": "Roll",
+  "race": "Race",
+  "classTitle": "Class",
+  "percentComplete": "{percent}% complete"
+}