feat(accessibility): add reduceMotion scaling and minimize animations; apply RepaintBoundary to heavy widgets

lib/widgets/analysis/monthly_expense_chart_card.dart

@@ -8,6 +8,7 @@ import '../../theme/app_colors.dart';
 import '../glassmorphism_card.dart';
 import '../themed_text.dart';
 import '../../l10n/app_localizations.dart';
+import '../../utils/reduce_motion.dart';
 
 /// 월별 지출 현황을 차트로 보여주는 카드 위젯
 class MonthlyExpenseChartCard extends StatelessWidget {
@@ -250,6 +251,10 @@ class MonthlyExpenseChartCard extends StatelessWidget {
                               ),
                             ),
                           ),
+                          swapAnimationDuration: ReduceMotion.isEnabled(context)
+                              ? const Duration(milliseconds: 0)
+                              : const Duration(milliseconds: 300),
+                          swapAnimationCurve: Curves.easeOut,
                         ),
                       ),
                     ),