feat(reward): 新增客户端奖励中心

test/player/player_center_toggle_test.dart

@@ -35,13 +35,19 @@ void main() {
       Key('player-play-toggle'),
     ]) {
       expect(tester.getSize(find.byKey(key)), const Size(68, 68));
-      // 圆形深色底：压在亮画面上也能看见播放/暂停。
-      final container = tester.widget<Container>(
-        find.descendant(of: find.byKey(key), matching: find.byType(Container)),
+      // 半透明玻璃圆面：压在亮画面上也能看见播放/暂停。
+      final surface = tester.widget<DecoratedBox>(
+        find
+            .descendant(
+              of: find.byKey(key),
+              matching: find.byKey(const Key('player-center-toggle-surface')),
+            )
+            .first,
       );
-      final decoration = container.decoration! as BoxDecoration;
-      expect(decoration.color, const Color(0x66000000));
+      final decoration = surface.decoration as BoxDecoration;
+      expect(decoration.gradient, isA<RadialGradient>());
       expect(decoration.shape, BoxShape.circle);
+      expect(decoration.border, isNull);
       final icon = tester.widget<Icon>(
         find.descendant(of: find.byKey(key), matching: find.byType(Icon)),
       );