修复安卓手机显示名称不符显示为linux的问题；修复文件名乱码的问题

backend/internal/handler/http.go

@@ -456,6 +456,7 @@ func (h *HTTPHandler) downloadFallback(c *gin.Context) {
 	defer cancel()
 
 	filename := filepath.Base(transfer.Name)
+	filename = decodeDownloadFilename(filename)
 	if filename == "." || filename == "" {
 		filename = "download.bin"
 	}
@@ -597,6 +598,19 @@ func contentDisposition(filename string) string {
 	return `attachment; filename="` + escaped + `"`
 }
 
+func decodeDownloadFilename(filename string) string {
+	filename = strings.TrimSpace(filename)
+	if filename == "" || !strings.Contains(filename, "%") {
+		return filename
+	}
+
+	decoded, err := url.PathUnescape(filename)
+	if err != nil {
+		return filename
+	}
+	return strings.TrimSpace(decoded)
+}
+
 func (h *HTTPHandler) ensureFallbackBucket(ctx context.Context, transferID string) error {
 	if h.deps.MinIOClient == nil {
 		return nil