optimize export sync plans, and clear too many sync plans

src/langs/zh_cn.json

@@ -39,6 +39,9 @@
   "command_startsync": "开始同步（start sync）",
   "command_drynrun": "开始同步（空跑模式）（start sync (dry run only)）",
   "command_exportsyncplans_json": "导出同步计划为 json 格式（export sync plans in json format）",
+  "command_exportsyncplans_1": "导出同步计划（最近 1 次）（export sync plans (latest 1)）",
+  "command_exportsyncplans_5": "导出同步计划（最近 5 次）（export sync plans (latest 5)）",
+  "command_exportsyncplans_all": "导出同步计划（所有）（export sync plans (all)）",
   "command_exportlogsindb": "从数据库导出终端日志（export logs saved in db）",
 
   "statusbar_time_years": "{{time}} 年前同步",
@@ -291,7 +294,9 @@
   "settings_viewconsolelog_desc": "电脑上，输入“ctrl+shift+i”或“cmd+shift+i”来查看终端输出。手机上，安装第三方插件 <a href='https://obsidian.md/plugins?search=Logstravaganza'>Logstravaganza</a> 来导出终端输出到一篇笔记上。",
   "settings_syncplans": "导出同步计划",
   "settings_syncplans_desc": "每次您启动同步，并在实际上传下载前，插件会生成同步计划。它可以使您知道每次同步发生了什么。点击按钮可以导出同步计划。",
-  "settings_syncplans_button_json": "导出",
+  "settings_syncplans_button_1": "导出最近 1 次",
+  "settings_syncplans_button_5": "导出最近 5 次",
+  "settings_syncplans_button_all": "导出所有",
   "settings_syncplans_notice": "同步计划已导出",
   "settings_delsyncplans": "删除数据库里的同步计划历史",
   "settings_delsyncplans_desc": "删除数据库里的同步计划历史。",