fix: 修复备份工具的多处问题

- go.mod: 将非法版本号 go 1.26.4 改为 go 1.26
- engine: 压缩失败时删除残留的半截 tar.gz 文件
- config: 支持仅按天数保留(count 和 days 均未设时才用默认 count=7)
- engine: docker compose stop 失败时也尝试重启,避免容器停摆
- list: 仅显示真正的备份归档文件(新增导出 IsBackupArchive)
- systemd: 移除 PrivateTmp,暂存目录改到安装目录内,避免私有 /tmp 被大目录撑爆

docker-compose-backup.service

@@ -19,8 +19,11 @@ User=root
 NoNewPrivileges=yes
 ProtectSystem=strict
 ProtectHome=yes
-ReadWritePaths=/opt/docker-compose-backup /tmp
-PrivateTmp=yes
+# The backup copies whole project directories into a staging area before
+# compressing. Keep staging inside the writable install dir (see temp_dir in
+# config.yaml) rather than /tmp, and do NOT use PrivateTmp — a private /tmp is
+# often small/tmpfs-backed and can be exhausted by large project copies.
+ReadWritePaths=/opt/docker-compose-backup
 ProtectKernelTunables=yes
 ProtectKernelModules=yes
 ProtectControlGroups=yes