feat: import Chinese-localized Buzz source snapshot

Signed-off-by: cls_宁波本机 <908705107@qq.com>

mobile/lib/features/channels/media_viewer_hero.dart

@@ -0,0 +1,72 @@
+import 'package:flutter/material.dart';
+
+/// Keeps image-viewer shared-element motion consistent at every source.
+class MediaViewerHero extends StatelessWidget {
+  /// The identity shared by the inline image and full-screen image.
+  final Object tag;
+
+  /// The image rendered during and after the shared-element transition.
+  final Widget child;
+
+  /// Creates an image-viewer shared element.
+  const MediaViewerHero({super.key, required this.tag, required this.child});
+
+  @override
+  Widget build(BuildContext context) {
+    return Hero(
+      tag: tag,
+      createRectTween: (begin, end) => RectTween(begin: begin, end: end),
+      flightShuttleBuilder:
+          (
+            flightContext,
+            animation,
+            flightDirection,
+            fromHeroContext,
+            toHeroContext,
+          ) {
+            final sourceHero = fromHeroContext.widget;
+            final destinationHero = toHeroContext.widget;
+            final sourceChild = sourceHero is Hero ? sourceHero.child : child;
+            final destinationChild = destinationHero is Hero
+                ? destinationHero.child
+                : child;
+            return _MediaViewerHeroFlight(
+              animation: animation,
+              sourceChild: sourceChild,
+              destinationChild: destinationChild,
+            );
+          },
+      child: child,
+    );
+  }
+}
+
+class _MediaViewerHeroFlight extends StatelessWidget {
+  final Animation<double> animation;
+  final Widget sourceChild;
+  final Widget destinationChild;
+
+  const _MediaViewerHeroFlight({
+    required this.animation,
+    required this.sourceChild,
+    required this.destinationChild,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final destinationOpacity = CurvedAnimation(
+      parent: animation,
+      curve: const Interval(0.18, 0.82, curve: Curves.easeInOutCubic),
+    );
+    return Stack(
+      fit: StackFit.expand,
+      children: [
+        FadeTransition(
+          opacity: ReverseAnimation(destinationOpacity),
+          child: sourceChild,
+        ),
+        FadeTransition(opacity: destinationOpacity, child: destinationChild),
+      ],
+    );
+  }
+}