fix(ui): 骨架屏改为逐卡片扫光

lib/core/widgets/drama_grid_skeleton.dart

@@ -11,6 +11,7 @@ const Duration _shimmerPeriod = Duration(milliseconds: 1400);
 const double _shimmerTravel = 2.4;
 const double _shimmerStart = -1.2;
 const double _subtitleWidthFactor = 0.62;
+const double _shimmerPhaseStep = 0.13;
 const Color _shimmerHighlight = Color(0x12FFFFFF);
 
 /// 首页短剧网格的占位。行数至少铺满可视高度，并带一道扫光。
@@ -53,21 +54,19 @@ class _DramaGridSkeletonState extends State<DramaGridSkeleton>
   Widget build(BuildContext context) {
     return LayoutBuilder(
       builder: (context, constraints) {
-        final grid = _grid(constraints.maxWidth, constraints.maxHeight);
         return AnimatedBuilder(
           animation: _shimmer,
-          builder: (context, child) => ShaderMask(
-            blendMode: BlendMode.srcATop,
-            shaderCallback: (bounds) => _shader(bounds),
-            child: child,
+          builder: (context, _) => _grid(
+            constraints.maxWidth,
+            constraints.maxHeight,
+            _shimmer.value,
           ),
-          child: grid,
         );
       },
     );
   }
 
-  Widget _grid(double width, double height) {
+  Widget _grid(double width, double height, double shimmerValue) {
     final itemWidth = _itemWidth(width);
     final itemExtent = _itemExtent(itemWidth);
     return GridView.builder(
@@ -85,7 +84,8 @@ class _DramaGridSkeletonState extends State<DramaGridSkeleton>
         mainAxisExtent: itemExtent,
       ),
       itemCount: _fillCount(height, itemExtent),
-      itemBuilder: (context, index) => _SkeletonCard(index: index),
+      itemBuilder: (context, index) =>
+          _SkeletonCard(index: index, shimmerValue: shimmerValue),
     );
   }
 
@@ -105,48 +105,54 @@ class _DramaGridSkeletonState extends State<DramaGridSkeleton>
     final rows = (height / rowHeight).ceil() + 1;
     return math.max(widget.itemCount, rows * widget.columns);
   }
-
-  Shader _shader(Rect bounds) {
-    final shift = _shimmerStart + _shimmerTravel * _shimmer.value;
-    return LinearGradient(
-      begin: Alignment(shift, -0.3),
-      end: Alignment(shift + 1, 0.3),
-      colors: const [
-        AppColors.skeletonSurface,
-        _shimmerHighlight,
-        AppColors.skeletonSurface,
-      ],
-    ).createShader(bounds);
-  }
 }
 
 class _SkeletonCard extends StatelessWidget {
-  const _SkeletonCard({required this.index});
+  const _SkeletonCard({required this.index, required this.shimmerValue});
 
   final int index;
+  final double shimmerValue;
 
   @override
   Widget build(BuildContext context) {
-    return Column(
-      key: Key('drama-grid-skeleton-$index'),
-      crossAxisAlignment: CrossAxisAlignment.start,
-      children: [
-        AspectRatio(
-          aspectRatio: AppDimens.cardCoverAspectRatio,
-          child: const _SkeletonBlock(),
-        ),
-        const SizedBox(height: AppDimens.cardCoverTitleGap),
-        const _SkeletonBar(),
-        const SizedBox(height: AppDimens.skeletonTitleBarGap),
-        const FractionallySizedBox(
-          widthFactor: _subtitleWidthFactor,
-          child: _SkeletonBar(),
-        ),
-      ],
+    final phase = (shimmerValue + index * _shimmerPhaseStep) % 1.0;
+    return ShaderMask(
+      blendMode: BlendMode.srcATop,
+      shaderCallback: (bounds) => _cardShader(bounds, phase),
+      child: Column(
+        key: Key('drama-grid-skeleton-$index'),
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          AspectRatio(
+            aspectRatio: AppDimens.cardCoverAspectRatio,
+            child: const _SkeletonBlock(),
+          ),
+          const SizedBox(height: AppDimens.cardCoverTitleGap),
+          const _SkeletonBar(),
+          const SizedBox(height: AppDimens.skeletonTitleBarGap),
+          const FractionallySizedBox(
+            widthFactor: _subtitleWidthFactor,
+            child: _SkeletonBar(),
+          ),
+        ],
+      ),
     );
   }
 }
 
+Shader _cardShader(Rect bounds, double shimmerValue) {
+  final shift = _shimmerStart + _shimmerTravel * shimmerValue;
+  return LinearGradient(
+    begin: Alignment(shift, -0.3),
+    end: Alignment(shift + 1, 0.3),
+    colors: const [
+      AppColors.skeletonSurface,
+      _shimmerHighlight,
+      AppColors.skeletonSurface,
+    ],
+  ).createShader(bounds);
+}
+
 class _SkeletonBlock extends StatelessWidget {
   const _SkeletonBlock();