feat: 다국어 지원 및 다중 통화 환율 변환 기능 확대

- ExchangeRateService에 JPY, CNY 환율 지원 추가
- 구독 서비스별 다국어 표시 이름 지원
- 분석 화면 차트 및 UI/UX 개선
- 설정 화면 전면 리팩토링
- SMS 스캔 기능 사용성 개선
- 전체 앱 다국어 번역 확대

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

lib/widgets/detail/detail_header_section.dart

@@ -3,7 +3,10 @@ import 'package:provider/provider.dart';
 import 'package:intl/intl.dart';
 import '../../models/subscription_model.dart';
 import '../../controllers/detail_screen_controller.dart';
+import '../../providers/locale_provider.dart';
+import '../../services/currency_util.dart';
 import '../website_icon.dart';
+import '../../l10n/app_localizations.dart';
 
 /// 상세 화면 상단 헤더 섹션
 /// 서비스 아이콘, 이름, 결제 정보를 표시합니다.
@@ -134,7 +137,7 @@ class DetailHeaderSection extends StatelessWidget {
                                   crossAxisAlignment: CrossAxisAlignment.start,
                                   children: [
                                     Text(
-                                      controller.serviceNameController.text,
+                                      controller.displayName ?? controller.serviceNameController.text,
                                       style: const TextStyle(
                                         fontSize: 28,
                                         fontWeight: FontWeight.w800,
@@ -151,7 +154,8 @@ class DetailHeaderSection extends StatelessWidget {
                                     ),
                                     const SizedBox(height: 4),
                                     Text(
-                                      '${controller.billingCycle} 결제',
+                                      AppLocalizations.of(context).billingCyclePayment.replaceAll('@', 
+                                        _getLocalizedBillingCycle(context, controller.billingCycle)),
                                       style: TextStyle(
                                         fontSize: 16,
                                         fontWeight: FontWeight.w500,
@@ -175,25 +179,28 @@ class DetailHeaderSection extends StatelessWidget {
                               mainAxisAlignment: MainAxisAlignment.spaceBetween,
                               children: [
                                 _InfoColumn(
-                                  label: '다음 결제일',
-                                  value: DateFormat('yyyy년 MM월 dd일')
-                                      .format(controller.nextBillingDate),
+                                  label: AppLocalizations.of(context).nextBillingDate,
+                                  value: AppLocalizations.of(context).formatDate(controller.nextBillingDate),
                                 ),
-                                _InfoColumn(
-                                  label: '월 지출',
-                                  value: NumberFormat.currency(
-                                    locale: controller.currency == 'KRW'
-                                        ? 'ko_KR'
-                                        : 'en_US',
-                                    symbol: controller.currency == 'KRW'
-                                        ? '₩'
-                                        : '\$',
-                                    decimalDigits:
-                                        controller.currency == 'KRW' ? 0 : 2,
-                                  ).format(double.tryParse(
-                                    controller.monthlyCostController.text.replaceAll(',', '')
-                                  ) ?? 0),
-                                  alignment: CrossAxisAlignment.end,
+                                FutureBuilder<String>(
+                                  future: () async {
+                                    final locale = context.read<LocaleProvider>().locale.languageCode;
+                                    final amount = double.tryParse(
+                                      controller.monthlyCostController.text.replaceAll(',', '')
+                                    ) ?? 0;
+                                    return CurrencyUtil.formatAmountWithLocale(
+                                      amount,
+                                      controller.currency,
+                                      locale,
+                                    );
+                                  }(),
+                                  builder: (context, snapshot) {
+                                    return _InfoColumn(
+                                      label: AppLocalizations.of(context).monthlyExpense,
+                                      value: snapshot.data ?? '-',
+                                      alignment: CrossAxisAlignment.end,
+                                    );
+                                  },
                                 ),
                               ],
                             ),
@@ -212,6 +219,33 @@ class DetailHeaderSection extends StatelessWidget {
       },
     );
   }
+  String _getLocalizedBillingCycle(BuildContext context, String cycle) {
+    final loc = AppLocalizations.of(context);
+    switch (cycle.toLowerCase()) {
+      case '매월':
+      case 'monthly':
+      case '毎月':
+      case '每月':
+        return loc.billingCycleMonthly;
+      case '분기별':
+      case 'quarterly':
+      case '四半期':
+      case '每季度':
+        return loc.billingCycleQuarterly;
+      case '반기별':
+      case 'half-yearly':
+      case '半年ごと':
+      case '每半年':
+        return loc.billingCycleHalfYearly;
+      case '매년':
+      case 'yearly':
+      case '年間':
+      case '每年':
+        return loc.billingCycleYearly;
+      default:
+        return cycle;
+    }
+  }
 }
 
 /// 정보 표시 컬럼