fix: 修复写队列 busy 恢复、关闭安全、备份与配置构建问题

internal/store/disk_unix.go

@@ -0,0 +1,13 @@
+//go:build unix
+
+package store
+
+import "golang.org/x/sys/unix"
+
+func availableBytes(path string) (uint64, error) {
+	var st unix.Statfs_t
+	if err := unix.Statfs(path, &st); err != nil {
+		return 0, err
+	}
+	return uint64(st.Bavail) * uint64(st.Bsize), nil
+}