feat(phase5): 종족/클래스 시스템 균형 및 UI 통합

- 21개 종족 균형 재설계 (스탯 합계 = 0)
- 18개 클래스 균형 재설계 (스탯 합계 = +3)
- Traits에 raceId, classId 필드 추가
- 저장/불러오기에 종족/클래스 ID 추가
- 캐릭터 생성 UI에서 RaceData/ClassData 사용
- 선택 시 스탯 보정 및 패시브 정보 표시

lib/data/class_data.dart

@@ -12,7 +12,7 @@ class ClassData {
   // 전사 계열 (STR 기반)
   // ==========================================================================
 
-  /// Bug Hunter: STR + INT
+  /// Bug Hunter: STR + INT (스탯 합계: +3)
   static const bugHunter = ClassTraits(
     classId: 'bug_hunter',
     name: 'Bug Hunter',
@@ -32,12 +32,13 @@ class ClassData {
     restriction: EquipmentRestriction.none,
   );
 
-  /// Overflow Warrior: STR
+  /// Overflow Warrior: STR + CON (스탯 합계: +3)
   static const overflowWarrior = ClassTraits(
     classId: 'overflow_warrior',
     name: 'Overflow Warrior',
     statModifiers: {
       StatType.str: 2,
+      StatType.con: 1,
     },
     startingSkills: ['power_strike'],
     classSkills: ['power_strike', 'overflow_slash', 'buffer_break'],
@@ -51,7 +52,7 @@ class ClassData {
     restriction: EquipmentRestriction.none,
   );
 
-  /// Stack Crusher: STR + CON
+  /// Stack Crusher: STR + CON (스탯 합계: +3)
   static const stackCrusher = ClassTraits(
     classId: 'stack_crusher',
     name: 'Stack Crusher',
@@ -76,7 +77,7 @@ class ClassData {
     restriction: EquipmentRestriction.none,
   );
 
-  /// Assertion Knight: STR + WIS
+  /// Assertion Knight: STR + WIS (스탯 합계: +3)
   static const assertionKnight = ClassTraits(
     classId: 'assertion_knight',
     name: 'Assertion Knight',
@@ -102,7 +103,7 @@ class ClassData {
   // 탱커 계열 (CON 기반)
   // ==========================================================================
 
-  /// Debugger Paladin: WIS + CON
+  /// Debugger Paladin: WIS + CON (스탯 합계: +3)
   static const debuggerPaladin = ClassTraits(
     classId: 'debugger_paladin',
     name: 'Debugger Paladin',
@@ -129,12 +130,13 @@ class ClassData {
     ),
   );
 
-  /// Loop Breaker: CON
+  /// Loop Breaker: CON + STR (스탯 합계: +3)
   static const loopBreaker = ClassTraits(
     classId: 'loop_breaker',
     name: 'Loop Breaker',
     statModifiers: {
       StatType.con: 2,
+      StatType.str: 1,
     },
     startingSkills: ['shield_bash'],
     classSkills: ['shield_bash', 'infinite_guard', 'break_stance'],
@@ -150,7 +152,7 @@ class ClassData {
     ),
   );
 
-  /// Garbage Collector: CON + STR
+  /// Garbage Collector: CON + STR (스탯 합계: +3)
   static const garbageCollector = ClassTraits(
     classId: 'garbage_collector',
     name: 'Garbage Collector',
@@ -181,12 +183,13 @@ class ClassData {
   // 마법사 계열 (INT 기반)
   // ==========================================================================
 
-  /// Compiler Mage: INT + MP Max
+  /// Compiler Mage: INT + WIS (스탯 합계: +3)
   static const compilerMage = ClassTraits(
     classId: 'compiler_mage',
     name: 'Compiler Mage',
     statModifiers: {
       StatType.intelligence: 2,
+      StatType.wis: 1,
     },
     startingSkills: ['fireball'],
     classSkills: ['fireball', 'compile_blast', 'syntax_storm'],
@@ -202,12 +205,13 @@ class ClassData {
     ),
   );
 
-  /// Recursion Master: INT
+  /// Recursion Master: INT + DEX (스탯 합계: +3)
   static const recursionMaster = ClassTraits(
     classId: 'recursion_master',
     name: 'Recursion Master',
     statModifiers: {
       StatType.intelligence: 2,
+      StatType.dex: 1,
     },
     startingSkills: ['fireball'],
     classSkills: ['fireball', 'recursive_bolt', 'stack_overflow'],
@@ -223,7 +227,7 @@ class ClassData {
     ),
   );
 
-  /// Memory Leaker: INT + WIS
+  /// Memory Leaker: INT + WIS (스탯 합계: +3)
   static const memoryLeaker = ClassTraits(
     classId: 'memory_leaker',
     name: 'Memory Leaker',
@@ -245,7 +249,7 @@ class ClassData {
     ),
   );
 
-  /// Type Caster: INT + CHA
+  /// Type Caster: INT + CHA (스탯 합계: +3)
   static const typeCaster = ClassTraits(
     classId: 'type_caster',
     name: 'Type Caster',
@@ -267,7 +271,7 @@ class ClassData {
     ),
   );
 
-  /// DevOps Shaman: CON + INT
+  /// DevOps Shaman: CON + INT (스탯 합계: +3)
   static const devOpsShaman = ClassTraits(
     classId: 'devops_shaman',
     name: 'DevOps Shaman',
@@ -298,12 +302,13 @@ class ClassData {
   // 민첩 계열 (DEX 기반)
   // ==========================================================================
 
-  /// Refactor Monk: DEX
+  /// Refactor Monk: DEX + CON (스탯 합계: +3)
   static const refactorMonk = ClassTraits(
     classId: 'refactor_monk',
     name: 'Refactor Monk',
     statModifiers: {
       StatType.dex: 2,
+      StatType.con: 1,
     },
     startingSkills: ['flurry'],
     classSkills: ['flurry', 'clean_code_strike', 'refactor_combo'],
@@ -324,12 +329,13 @@ class ClassData {
     ),
   );
 
-  /// Pointer Assassin: DEX
+  /// Pointer Assassin: DEX + STR (스탯 합계: +3)
   static const pointerAssassin = ClassTraits(
     classId: 'pointer_assassin',
     name: 'Pointer Assassin',
     statModifiers: {
       StatType.dex: 2,
+      StatType.str: 1,
     },
     startingSkills: ['backstab'],
     classSkills: ['backstab', 'null_strike', 'dereference_kill'],
@@ -350,7 +356,7 @@ class ClassData {
     ),
   );
 
-  /// Callback Samurai: DEX + STR
+  /// Callback Samurai: DEX + STR (스탯 합계: +3)
   static const callbackSamurai = ClassTraits(
     classId: 'callback_samurai',
     name: 'Callback Samurai',
@@ -375,7 +381,7 @@ class ClassData {
     restriction: EquipmentRestriction.none,
   );
 
-  /// Tester Jester: DEX + CHA
+  /// Tester Jester: DEX + CHA (스탯 합계: +3)
   static const testerJester = ClassTraits(
     classId: 'tester_jester',
     name: 'Tester Jester',
@@ -406,12 +412,13 @@ class ClassData {
   // 지혜 계열 (WIS 기반)
   // ==========================================================================
 
-  /// Exception Handler: WIS
+  /// Exception Handler: WIS + INT (스탯 합계: +3)
   static const exceptionHandler = ClassTraits(
     classId: 'exception_handler',
     name: 'Exception Handler',
     statModifiers: {
       StatType.wis: 2,
+      StatType.intelligence: 1,
     },
     startingSkills: ['heal'],
     classSkills: ['heal', 'try_catch', 'finally_heal'],
@@ -427,7 +434,7 @@ class ClassData {
     ),
   );
 
-  /// Null Checker: WIS + INT
+  /// Null Checker: WIS + INT (스탯 합계: +3)
   static const nullChecker = ClassTraits(
     classId: 'null_checker',
     name: 'Null Checker',