refactor(ui): 화면 UI 정리

- front_screen: 프론트 화면 레이아웃 개선
- settings_screen: 설정 화면 간소화
- new_character_screen: 캐릭터 생성 화면 정리

lib/src/features/front/front_screen.dart

@@ -321,8 +321,8 @@ class _ActionButtons extends StatelessWidget {
             onPressed: onSettings,
             isPrimary: false,
           ),
-          // IAP 구매 (광고 제거) - 스토어 사용 가능하고 미구매 상태일 때만 표시
-          if (removeAdsPrice != null && !isAdRemovalPurchased) ...[
+          // IAP 구매 (광고 제거) - 스토어 사용 가능할 때 표시 (구매 완료 시 비활성화)
+          if (removeAdsPrice != null) ...[
             const SizedBox(height: 20),
             const Divider(color: RetroColors.panelBorderInner, height: 1),
             const SizedBox(height: 12),
@@ -330,13 +330,12 @@ class _ActionButtons extends StatelessWidget {
               price: removeAdsPrice!,
               onPurchase: onPurchaseRemoveAds,
               onRestore: onRestorePurchase,
+              enabled: !isAdRemovalPurchased,
             ),
           ],
-          // 이미 구매된 경우 표시
+          // 이미 구매된 경우 배지 표시
           if (isAdRemovalPurchased) ...[
-            const SizedBox(height: 20),
-            const Divider(color: RetroColors.panelBorderInner, height: 1),
-            const SizedBox(height: 12),
+            const SizedBox(height: 8),
             _PurchasedBadge(),
           ],
         ],
@@ -412,11 +411,13 @@ class _IapPurchaseButton extends StatelessWidget {
     required this.price,
     this.onPurchase,
     this.onRestore,
+    this.enabled = true,
   });
 
   final String price;
   final VoidCallback? onPurchase;
   final VoidCallback? onRestore;
+  final bool enabled;
 
   void _showPurchaseDialog(BuildContext context) {
     showDialog<void>(
@@ -433,23 +434,33 @@ class _IapPurchaseButton extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    // 비활성화 상태의 색상
+    final buttonColor = enabled ? RetroColors.gold : RetroColors.textDisabled;
+    final bgGradient = enabled
+        ? const LinearGradient(
+            colors: [Color(0xFF4A3B2A), Color(0xFF3D2E1F)],
+            begin: Alignment.topCenter,
+            end: Alignment.bottomCenter,
+          )
+        : const LinearGradient(
+            colors: [Color(0xFF3A3A3A), Color(0xFF2A2A2A)],
+            begin: Alignment.topCenter,
+            end: Alignment.bottomCenter,
+          );
+
     return Column(
       crossAxisAlignment: CrossAxisAlignment.stretch,
       children: [
         // 구매 버튼 (클릭 시 팝업)
         Container(
           decoration: BoxDecoration(
-            gradient: const LinearGradient(
-              colors: [Color(0xFF4A3B2A), Color(0xFF3D2E1F)],
-              begin: Alignment.topCenter,
-              end: Alignment.bottomCenter,
-            ),
-            border: Border.all(color: RetroColors.gold, width: 2),
+            gradient: bgGradient,
+            border: Border.all(color: buttonColor, width: 2),
           ),
           child: Material(
             color: Colors.transparent,
             child: InkWell(
-              onTap: () => _showPurchaseDialog(context),
+              onTap: enabled ? () => _showPurchaseDialog(context) : null,
               child: Padding(
                 padding: const EdgeInsets.symmetric(
                   horizontal: 16,
@@ -457,7 +468,7 @@ class _IapPurchaseButton extends StatelessWidget {
                 ),
                 child: Row(
                   children: [
-                    const Icon(Icons.block, color: RetroColors.gold, size: 24),
+                    Icon(Icons.block, color: buttonColor, size: 24),
                     const SizedBox(width: 12),
                     Expanded(
                       child: Column(
@@ -465,10 +476,10 @@ class _IapPurchaseButton extends StatelessWidget {
                         children: [
                           Text(
                             game_l10n.iapRemoveAds,
-                            style: const TextStyle(
+                            style: TextStyle(
                               fontFamily: 'PressStart2P',
                               fontSize: 12,
-                              color: RetroColors.gold,
+                              color: buttonColor,
                             ),
                           ),
                           const SizedBox(height: 4),
@@ -484,11 +495,7 @@ class _IapPurchaseButton extends StatelessWidget {
                       ),
                     ),
                     // 화살표 아이콘 (상세 보기)
-                    const Icon(
-                      Icons.arrow_forward_ios,
-                      color: RetroColors.gold,
-                      size: 16,
-                    ),
+                    Icon(Icons.arrow_forward_ios, color: buttonColor, size: 16),
                   ],
                 ),
               ),
@@ -499,7 +506,7 @@ class _IapPurchaseButton extends StatelessWidget {
         // 복원 버튼
         Center(
           child: TextButton(
-            onPressed: onRestore,
+            onPressed: enabled ? onRestore : null,
             child: Text(
               game_l10n.iapRestorePurchase,
               style: const TextStyle(
@@ -569,7 +576,10 @@ class _IapPurchaseDialog extends StatelessWidget {
               const SizedBox(height: 8),
               _BenefitItem(icon: Icons.speed, text: game_l10n.iapBenefit5),
               const SizedBox(height: 8),
-              _BenefitItem(icon: Icons.inventory_2, text: game_l10n.iapBenefit6),
+              _BenefitItem(
+                icon: Icons.inventory_2,
+                text: game_l10n.iapBenefit6,
+              ),
               const SizedBox(height: 20),
               // 가격 + 구매 버튼
               Container(