feat: SMS 스캔 화면 리팩토링 및 MVC 패턴 적용

- SMS 스캔 화면을 컨트롤러/서비스/위젯으로 분리
- 코드 가독성 및 유지보수성 향상
- 새로운 다국어 지원 키 추가
- Git 커밋 가이드라인 문서화

lib/widgets/sms_scan/scan_progress_widget.dart

@@ -0,0 +1,38 @@
+import 'package:flutter/material.dart';
+import '../../theme/app_colors.dart';
+import '../../widgets/themed_text.dart';
+
+class ScanProgressWidget extends StatelessWidget {
+  final int currentIndex;
+  final int totalCount;
+
+  const ScanProgressWidget({
+    super.key,
+    required this.currentIndex,
+    required this.totalCount,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.stretch,
+      children: [
+        // 진행 상태 표시
+        LinearProgressIndicator(
+          value: (currentIndex + 1) / totalCount,
+          backgroundColor: AppColors.navyGray.withValues(alpha: 0.2),
+          valueColor: AlwaysStoppedAnimation<Color>(
+            Theme.of(context).colorScheme.primary,
+          ),
+        ),
+        const SizedBox(height: 8),
+        ThemedText(
+          '${currentIndex + 1}/$totalCount',
+          fontWeight: FontWeight.w500,
+          opacity: 0.7,
+          forceDark: true,
+        ),
+      ],
+    );
+  }
+}