refactor(empty-state): 空状态支持内容居中

lib/pages/favorites/favorites_page.dart

@@ -38,7 +38,6 @@ const double _synopsisFontSize = 12;
 const double _synopsisLineHeight = 1.15;
 const double _synopsisGap = 4;
 const int _maxTags = 2;
-const double _emptyListHeight = 360;
 const double _loadMoreThreshold = 240;
 
 final RegExp _tagSplitter = RegExp(r'[,/、·]');
@@ -124,37 +123,29 @@ class _FavoritesBody extends StatelessWidget {
       );
     }
     if (favorites.error != null && favorites.cards.isEmpty) {
-      return _refreshable(
+      return _refreshableState(
         favorites,
-        children: [
-          SizedBox(
-            height: _emptyListHeight,
-            child: EmptyState(
-              key: const Key('favorites-error'),
-              icon: Icons.cloud_off_rounded,
-              title: errorText(l10n, favorites.error, l10n.favoritesError),
-              actionLabel: l10n.retry,
-              actionKey: const Key('favorites-retry'),
-              onAction: () => unawaited(favorites.load()),
-            ),
-          ),
-        ],
+        child: EmptyState(
+          key: const Key('favorites-error'),
+          icon: Icons.cloud_off_rounded,
+          title: errorText(l10n, favorites.error, l10n.favoritesError),
+          actionLabel: l10n.retry,
+          actionKey: const Key('favorites-retry'),
+          onAction: () => unawaited(favorites.load()),
+          stretchContent: true,
+        ),
       );
     }
     if (favorites.cards.isEmpty) {
-      return _refreshable(
+      return _refreshableState(
         favorites,
-        children: [
-          SizedBox(
-            height: _emptyListHeight,
-            child: EmptyState(
-              key: const Key('favorites-empty'),
-              icon: Icons.star_border_rounded,
-              title: l10n.noFavorites,
-              subtitle: l10n.emptyHint,
-            ),
-          ),
-        ],
+        child: EmptyState(
+          key: const Key('favorites-empty'),
+          icon: Icons.star_border_rounded,
+          title: l10n.noFavorites,
+          subtitle: l10n.emptyHint,
+          stretchContent: true,
+        ),
       );
     }
     return _refreshable(
@@ -205,6 +196,20 @@ class _FavoritesBody extends StatelessWidget {
     );
   }
 
+  Widget _refreshableState(
+    FavoriteController favorites, {
+    required Widget child,
+  }) {
+    return AppPullToRefresh(
+      onRefresh: favorites.load,
+      child: CustomScrollView(
+        key: const Key('favorites-empty-scroll'),
+        physics: AppPullToRefresh.physics,
+        slivers: [SliverFillRemaining(hasScrollBody: false, child: child)],
+      ),
+    );
+  }
+
   bool _onScroll(ScrollNotification notification) {
     if (notification.depth != 0) return false;
     final reachedBottom =