更新数据目录配置

bin/util/vips.dart

@@ -4,8 +4,9 @@ import 'package:path/path.dart';
 
 class Vips {
   String? vipsExecuteFile;
+  final String cacheDir;
 
-  Vips({this.vipsExecuteFile});
+  Vips({this.vipsExecuteFile, required this.cacheDir});
 
   /// 生成图片预览（WebP 格式）
   /// 
@@ -22,7 +23,7 @@ class Vips {
     // 生成缓存文件名：包含原图 hash 和尺寸信息
     final baseName = basename(imgPath).hashCode.toString();
     final sizeSuffix = _buildSizeSuffix(w, h);
-    final imgOut = "cache/preview/${baseName}${sizeSuffix}.webp";
+    final imgOut = "$cacheDir/preview/$baseName$sizeSuffix.webp";
     final outFile = File(imgOut);
     
     // 缓存命中：直接返回已存在的预览图