perf(ui): enable KeepAlive on subscription list, tune prefetch, and reduce list/gesture animations

lib/widgets/swipeable_subscription_card.dart

@@ -2,12 +2,14 @@ import 'package:flutter/material.dart';
 import '../models/subscription_model.dart';
 import '../utils/haptic_feedback_helper.dart';
 import 'subscription_card.dart';
+import '../utils/reduce_motion.dart';
 
 class SwipeableSubscriptionCard extends StatefulWidget {
   final SubscriptionModel subscription;
   final VoidCallback? onEdit;
   final Future<void> Function()? onDelete;
   final VoidCallback? onTap;
+  final bool keepAlive;
 
   const SwipeableSubscriptionCard({
     super.key,
@@ -15,6 +17,7 @@ class SwipeableSubscriptionCard extends StatefulWidget {
     this.onEdit,
     this.onDelete,
     this.onTap,
+    this.keepAlive = false,
   });
 
   @override
@@ -23,7 +26,7 @@ class SwipeableSubscriptionCard extends StatefulWidget {
 }
 
 class _SwipeableSubscriptionCardState extends State<SwipeableSubscriptionCard>
-    with SingleTickerProviderStateMixin {
+    with SingleTickerProviderStateMixin, AutomaticKeepAliveClientMixin {
   // 상수 정의
   static const double _tapTolerance = 20.0; // 탭 허용 범위
   static const double _actionThresholdPercent = 0.15;
@@ -49,7 +52,9 @@ class _SwipeableSubscriptionCardState extends State<SwipeableSubscriptionCard>
   void initState() {
     super.initState();
     _controller = AnimationController(
-      duration: const Duration(milliseconds: 300),
+      duration: ReduceMotion.platform()
+          ? const Duration(milliseconds: 0)
+          : const Duration(milliseconds: 300),
       vsync: this,
     );
     _animation = Tween<double>(
@@ -215,10 +220,14 @@ class _SwipeableSubscriptionCardState extends State<SwipeableSubscriptionCard>
         right: isLeft ? 0 : 24,
       ),
       child: AnimatedOpacity(
-        duration: const Duration(milliseconds: 200),
+        duration: ReduceMotion.platform()
+            ? const Duration(milliseconds: 0)
+            : const Duration(milliseconds: 200),
         opacity: showIcon ? 1.0 : 0.0,
         child: AnimatedScale(
-          duration: const Duration(milliseconds: 200),
+          duration: ReduceMotion.platform()
+              ? const Duration(milliseconds: 0)
+              : const Duration(milliseconds: 200),
           scale: showIcon ? 1.0 : 0.5,
           child: Icon(
             isDeleteThreshold
@@ -236,9 +245,10 @@ class _SwipeableSubscriptionCardState extends State<SwipeableSubscriptionCard>
     return Transform.translate(
       offset: Offset(_currentOffset, 0),
       child: Transform.scale(
-        scale: 1.0 - (_currentOffset.abs() / 2000),
+        scale:
+            ReduceMotion.platform() ? 1.0 : 1.0 - (_currentOffset.abs() / 2000),
         child: Transform.rotate(
-          angle: _currentOffset / 2000,
+          angle: ReduceMotion.platform() ? 0.0 : _currentOffset / 2000,
           child: SubscriptionCard(
             subscription: widget.subscription,
             onTap: widget
@@ -251,6 +261,7 @@ class _SwipeableSubscriptionCardState extends State<SwipeableSubscriptionCard>
 
   @override
   Widget build(BuildContext context) {
+    super.build(context);
     // 웹과 모바일 모두 동일한 스와이프 기능 제공
     return Stack(
       children: [
@@ -266,4 +277,7 @@ class _SwipeableSubscriptionCardState extends State<SwipeableSubscriptionCard>
       ],
     );
   }
+
+  @override
+  bool get wantKeepAlive => widget.keepAlive;
 }