feat(flutter): 增加轮播自动播放与站内通知

lib/core/widgets/remote_image.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 
 import '../config/app_config.dart';
+import '../theme/app_colors.dart';
 
 /// 封面图统一入口：后端给的是相对路径，这里补服务地址并处理加载失败。
 class RemoteImage extends StatelessWidget {
@@ -10,12 +11,16 @@ class RemoteImage extends StatelessWidget {
     this.width,
     this.height,
     this.fit = BoxFit.cover,
+    this.showFallbackIcon = false,
+    this.fallbackIconKey,
   });
 
   final String path;
   final double? width;
   final double? height;
   final BoxFit fit;
+  final bool showFallbackIcon;
+  final Key? fallbackIconKey;
 
   @override
   Widget build(BuildContext context) {
@@ -38,7 +43,16 @@ class RemoteImage extends StatelessWidget {
     return Container(
       width: width,
       height: height,
-      color: const Color(0xFF1C1F26),
+      color: AppColors.bar,
+      alignment: Alignment.center,
+      child: showFallbackIcon
+          ? Icon(
+              Icons.image_not_supported_outlined,
+              key: fallbackIconKey,
+              color: AppColors.muted,
+              size: 32,
+            )
+          : null,
     );
   }
 }