feat: manage extensions navbar (#2121)

* feat: manage extensions navbar
create now `Manage` spacer in sidebar. and add manage extensions to it
closes #2088
* do not show when no exts
* update cn and jp i18n strings
* rename lnbits-admin-ui component to lnbits-manage, fix its behaviour
* i18n: add Korean language

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Co-authored-by: Pavol Rusnak <pavol@rusnak.io>
Co-authored-by: psychoet <125599543+psychoet@users.noreply.github.com>

lnbits/static/i18n/cn.js

@@ -72,13 +72,12 @@ window.localisation.cn = {
   disclaimer_dialog:
     '登录功能将在以后的更新中发布，请将此页面加为书签，以便将来访问您的钱包！此服务处于测试阶段，我们不对资金的丢失承担任何责任。',
   no_transactions: '尚未进行任何交易',
-  manage_server: '管理服务器',
+  manage: '管理',
   extensions: '扩展程序',
   no_extensions: '你没有安装任何扩展程序 :(',
   created: '已创建',
   search_extensions: '搜索扩展程序',
   warning: '警告',
-  manage: '管理',
   repository: '代码库',
   confirm_continue: '你确定要继续吗?',
   manage_extension_details: '安装/卸载扩展程序',