perf(player): 续看点加载与进度写盘改为并行且复用同一请求

进播放页与首次准备播放会各要一次续看点，同一次请求跑两遍还串在首帧前；
现在并发请求复用同一 Future，并与上一条进度写盘并行等待，少一个网络往返的起播延迟。
剧场网格海报按布局宽度限制解码尺寸，半屏卡片不再按原图解码。

lib/pages/discover/widgets/drama_grid.dart

@@ -7,6 +7,7 @@ import '../../../core/data/models/drama.dart';
 import '../../../core/formatting/count_format.dart';
 import '../../../core/theme/app_colors.dart';
 import '../../../core/theme/app_dimens.dart';
+import '../../../core/widgets/remote_image.dart';
 import '../../../l10n/app_localizations.dart';
 
 const int _columns = 2;
@@ -218,16 +219,28 @@ class _DiscoverCoverImage extends StatelessWidget {
   Widget build(BuildContext context) {
     final url = AppConfig.mediaUrl(path);
     if (url.isEmpty) return _placeholder();
-    return Image.network(
-      url,
-      width: double.infinity,
-      height: double.infinity,
-      fit: BoxFit.cover,
-      loadingBuilder: (context, child, progress) {
-        if (progress == null) return child;
-        return _placeholder();
+    return LayoutBuilder(
+      builder: (context, constraints) {
+        // 卡片只有半屏宽，按原图解码一张竖版海报就是数 MB，按布局宽度限一下。
+        final decodeWidth = constraints.hasBoundedWidth
+            ? resolveImageDecodePixels(
+                constraints.maxWidth,
+                MediaQuery.devicePixelRatioOf(context),
+              )
+            : null;
+        return Image.network(
+          url,
+          width: double.infinity,
+          height: double.infinity,
+          fit: BoxFit.cover,
+          cacheWidth: decodeWidth,
+          loadingBuilder: (context, child, progress) {
+            if (progress == null) return child;
+            return _placeholder();
+          },
+          errorBuilder: (_, _, _) => _placeholder(),
+        );
       },
-      errorBuilder: (_, _, _) => _placeholder(),
     );
   }
 

lib/pages/player/player_logic.dart

@@ -110,6 +110,9 @@ class PlayerLogic extends ChangeNotifier {
   ResumePoint? resumePoint;
   bool resumeLoaded = false;
 
+  /// 续看点加载中的请求：进页与首次准备播放会同时触发，复用同一次请求。
+  Future<void>? _resumePointLoad;
+
   /// 票据三态：加载中 / 失败（可重试）/ 被后端判定为不可播放
   bool ticketLoading = false;
   String? ticketError;
@@ -512,7 +515,15 @@ class PlayerLogic extends ChangeNotifier {
   }
 
   /// 服务端续看位置：进播放页时取一次，用于"定位到上次那一集的那一秒"。
-  Future<void> loadResumePoint() async {
+  Future<void> loadResumePoint() {
+    final inFlight = _resumePointLoad;
+    if (inFlight != null) return inFlight;
+    return _resumePointLoad = _loadResumePoint().whenComplete(() {
+      _resumePointLoad = null;
+    });
+  }
+
+  Future<void> _loadResumePoint() async {
     final entry = queue.entryAt(initialIndex);
     final cached = positionCache.read(
       entry.episode.id,
@@ -1281,9 +1292,12 @@ class PlayerLogic extends ChangeNotifier {
         await _waitUntilFrameReady(player.controller);
         return;
       }
-      await pendingWrite;
+      // 上一条进度写盘与续看点拉取互不依赖，并行等，少一个网络往返的首帧延迟。
       // 服务端每剧只记一条：只有"记录里的那一集"才定位，其它集从头播
-      if (resumePoint == null) await loadResumePoint();
+      await Future.wait([
+        pendingWrite,
+        if (!resumeLoaded) loadResumePoint(),
+      ]);
       if (resumePositionFor(episode.id) == null) {
         final dramaId = _dramaIdForEpisode(episode.id);
         final cached = dramaId == null