fix(cover): 封面占位改为品牌标识

lib/core/widgets/remote_image.dart

@@ -31,34 +31,45 @@ class RemoteImage extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final url = AppConfig.mediaUrl(path);
-    if (url.isEmpty) return _fallback();
+    if (url.isEmpty) return _fallback(brand: showFallbackIcon);
     return Image.network(
       url,
       width: width,
       height: height,
       fit: fit,
-      errorBuilder: (_, _, _) => _fallback(),
+      gaplessPlayback: true,
+      errorBuilder: (_, _, _) => _fallback(brand: showFallbackIcon),
       frameBuilder: (context, child, frame, wasSynchronouslyLoaded) {
         if (wasSynchronouslyLoaded || frame != null) return child;
-        return _fallback();
+        return _fallback(brand: showFallbackIcon);
       },
     );
   }
 
-  Widget _fallback() {
+  Widget _fallback({required bool brand}) {
+    final mark = brand
+        ? LayoutBuilder(
+            builder: (context, constraints) {
+              final width = constraints.maxWidth.isFinite
+                  ? constraints.maxWidth
+                  : 120.0;
+              return Center(
+                child: Image.asset(
+                  'assets/icon/splash_logo.png',
+                  key: fallbackIconKey,
+                  width: width * 0.72,
+                  fit: BoxFit.contain,
+                ),
+              );
+            },
+          )
+        : null;
     final fallback = Container(
       width: width,
       height: height,
-      color: fallbackColor,
+      color: brand ? AppColors.mediaBlack : fallbackColor,
       alignment: Alignment.center,
-      child: showFallbackIcon
-          ? Icon(
-              Icons.image_not_supported_outlined,
-              key: fallbackIconKey,
-              color: AppColors.muted,
-              size: 32,
-            )
-          : null,
+      child: mark,
     );
     final ratio = fallbackAspectRatio;
     if (ratio == null) return fallback;