feat(core): i18n 및 핵심 로직 개선

- 수익화 관련 텍스트 추가
- item_service 수정
- progress_service 수정

lib/src/core/engine/item_service.dart

@@ -60,23 +60,26 @@ class ItemService {
   // 희귀도 결정
   // ============================================================================
 
-  /// 희귀도 결정 (레벨 기반 확률)
+  /// 희귀도 결정 (고정 확률)
   ///
-  /// 레벨이 높을수록 희귀한 아이템 확률 증가
+  /// 확률 분포:
+  /// - Common: 34%
+  /// - Uncommon: 40%
+  /// - Rare: 20%
+  /// - Epic: 5%
+  /// - Legendary: 1%
   ItemRarity determineRarity(int level) {
     final roll = rng.nextInt(100);
-    final legendaryChance = (level * 0.5).clamp(0, 5).toInt(); // 최대 5%
-    final epicChance = (level * 1.0).clamp(0, 10).toInt(); // 최대 10%
-    final rareChance = (level * 2.0).clamp(0, 20).toInt(); // 최대 20%
-    final uncommonChance = (level * 3.0).clamp(0, 30).toInt(); // 최대 30%
 
-    if (roll < legendaryChance) return ItemRarity.legendary;
-    if (roll < legendaryChance + epicChance) return ItemRarity.epic;
-    if (roll < legendaryChance + epicChance + rareChance)
-      return ItemRarity.rare;
-    if (roll < legendaryChance + epicChance + rareChance + uncommonChance) {
-      return ItemRarity.uncommon;
-    }
+    // Legendary: 0-0 (1%)
+    if (roll < 1) return ItemRarity.legendary;
+    // Epic: 1-5 (5%)
+    if (roll < 6) return ItemRarity.epic;
+    // Rare: 6-25 (20%)
+    if (roll < 26) return ItemRarity.rare;
+    // Uncommon: 26-65 (40%)
+    if (roll < 66) return ItemRarity.uncommon;
+    // Common: 66-99 (34%)
     return ItemRarity.common;
   }
 

lib/src/core/engine/progress_service.dart

@@ -972,12 +972,16 @@ class ProgressService {
     String? lostItemName;
     EquipmentSlot? lostItemSlot;
     ItemRarity? lostItemRarity;
+    EquipmentItem? lostEquipmentItem; // 광고 부활 시 복구용
 
     if (!isBossDeath) {
       // 레벨 기반 장비 손실 확률 계산
-      // Lv 1~5: 0%, Lv 6: 10%, Lv 10: 50%, Lv 15+: 100%
+      // Lv 1: 20%, Lv 5: ~56%, Lv 10+: 100%
+      // 공식: 20 + (level - 1) * 80 / 9
       final level = state.traits.level;
-      final lossChancePercent = ((level - 5) * 10).clamp(0, 100);
+      final lossChancePercent = level >= 10
+          ? 100
+          : (20 + ((level - 1) * 80 ~/ 9)).clamp(0, 100);
       final roll = state.rng.nextInt(100); // 0~99
       final shouldLoseEquipment = roll < lossChancePercent;
 
@@ -1004,10 +1008,10 @@ class ProgressService {
               )];
 
           // 제물로 바칠 아이템 정보 저장
-          final lostItem = state.equipment.getItemByIndex(sacrificeIndex);
-          lostItemName = lostItem.name;
+          lostEquipmentItem = state.equipment.getItemByIndex(sacrificeIndex);
+          lostItemName = lostEquipmentItem.name;
           lostItemSlot = EquipmentSlot.values[sacrificeIndex];
-          lostItemRarity = lostItem.rarity;
+          lostItemRarity = lostEquipmentItem.rarity;
 
           // 해당 슬롯을 빈 장비로 교체
           newEquipment = newEquipment.setItemByIndex(
@@ -1029,6 +1033,7 @@ class ProgressService {
       lostItemName: lostItemName,
       lostItemSlot: lostItemSlot,
       lostItemRarity: lostItemRarity,
+      lostItem: lostEquipmentItem, // 광고 부활 시 복구용
       goldAtDeath: state.inventory.gold,
       levelAtDeath: state.traits.level,
       timestamp: state.skillSystem.elapsedMs,