Initial commit: SubManager Flutter App

주요 구현 완료 기능:
- 구독 관리 (추가/편집/삭제/카테고리 분류)
- 이벤트 할인 시스템 (기본값 자동 설정)
- SMS 자동 스캔 및 구독 정보 추출
- 알림 시스템 (타임존 처리 안정화)
- 환율 변환 지원 (KRW/USD)
- 반응형 UI 및 애니메이션
- 다국어 지원 (한국어/영어)

버그 수정:
- NotificationService tz.local 초기화 오류 해결
- MainScreenSummaryCard 레이아웃 오버플로우 수정
- 구독 추가 시 LateInitializationError 완전 해결

🤖 Generated with Claude Code

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

lib/widgets/empty_state_widget.dart

@@ -0,0 +1,147 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+import 'dart:math' as math;
+
+/// 구독이 없을 때 표시되는 빈 화면 위젯
+///
+/// 애니메이션 효과와 함께 사용자에게 구독 추가를 유도합니다.
+class EmptyStateWidget extends StatelessWidget {
+  final AnimationController fadeController;
+  final AnimationController rotateController;
+  final AnimationController slideController;
+  final VoidCallback onAddPressed;
+
+  const EmptyStateWidget({
+    Key? key,
+    required this.fadeController,
+    required this.rotateController,
+    required this.slideController,
+    required this.onAddPressed,
+  }) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return FadeTransition(
+      opacity: Tween<double>(begin: 0.0, end: 1.0).animate(
+          CurvedAnimation(parent: fadeController, curve: Curves.easeIn)),
+      child: Center(
+        child: SlideTransition(
+          position: Tween<Offset>(
+            begin: const Offset(0, 0.2),
+            end: Offset.zero,
+          ).animate(CurvedAnimation(
+              parent: slideController, curve: Curves.easeOutBack)),
+          child: Container(
+            margin: const EdgeInsets.all(16),
+            padding: const EdgeInsets.all(32),
+            decoration: BoxDecoration(
+              color: Colors.white,
+              borderRadius: BorderRadius.circular(24),
+              boxShadow: [
+                BoxShadow(
+                  color: Colors.grey.withOpacity(0.08),
+                  spreadRadius: 0,
+                  blurRadius: 16,
+                  offset: const Offset(0, 8),
+                ),
+              ],
+            ),
+            child: Column(
+              mainAxisSize: MainAxisSize.min,
+              children: [
+                AnimatedBuilder(
+                  animation: rotateController,
+                  builder: (context, child) {
+                    return Transform.rotate(
+                      angle: rotateController.value * 2 * math.pi,
+                      child: Container(
+                        padding: const EdgeInsets.all(24),
+                        decoration: BoxDecoration(
+                          gradient: const LinearGradient(
+                            colors: [Color(0xFF3B82F6), Color(0xFF2563EB)],
+                            begin: Alignment.topLeft,
+                            end: Alignment.bottomRight,
+                          ),
+                          borderRadius: BorderRadius.circular(16),
+                          boxShadow: [
+                            BoxShadow(
+                              color: const Color(0xFF3B82F6).withOpacity(0.3),
+                              spreadRadius: 0,
+                              blurRadius: 16,
+                              offset: const Offset(0, 8),
+                            ),
+                          ],
+                        ),
+                        child: const Icon(
+                          Icons.subscriptions_outlined,
+                          size: 48,
+                          color: Colors.white,
+                        ),
+                      ),
+                    );
+                  },
+                ),
+                const SizedBox(height: 32),
+                ShaderMask(
+                  shaderCallback: (bounds) => const LinearGradient(
+                    colors: [Color(0xFF3B82F6), Color(0xFF0EA5E9)],
+                    begin: Alignment.topLeft,
+                    end: Alignment.bottomRight,
+                  ).createShader(bounds),
+                  child: const Text(
+                    '등록된 구독이 없습니다',
+                    style: TextStyle(
+                      fontSize: 22,
+                      fontWeight: FontWeight.w800,
+                      color: Colors.white,
+                      letterSpacing: -0.5,
+                    ),
+                  ),
+                ),
+                const SizedBox(height: 8),
+                const Text(
+                  '새로운 구독을 추가해보세요',
+                  style: TextStyle(
+                    fontSize: 16,
+                    color: Color(0xFF64748B),
+                  ),
+                ),
+                const SizedBox(height: 32),
+                MouseRegion(
+                  onEnter: (_) => {},
+                  onExit: (_) => {},
+                  child: ElevatedButton(
+                    style: ElevatedButton.styleFrom(
+                      foregroundColor: Colors.white,
+                      padding: const EdgeInsets.symmetric(
+                        horizontal: 32,
+                        vertical: 16,
+                      ),
+                      shape: RoundedRectangleBorder(
+                        borderRadius: BorderRadius.circular(16),
+                      ),
+                      elevation: 4,
+                      backgroundColor: const Color(0xFF3B82F6),
+                    ),
+                    onPressed: () {
+                      HapticFeedback.mediumImpact();
+                      onAddPressed();
+                    },
+                    child: const Text(
+                      '구독 추가하기',
+                      style: TextStyle(
+                        fontSize: 16,
+                        fontWeight: FontWeight.w600,
+                        letterSpacing: 0.5,
+                      ),
+                    ),
+                  ),
+                ),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}