feat(home): clarify 5chan is serverless app, use current hostname for share links

- Homepage infobox: merged copy into single line explaining app nature and download link
- Share links (Copy direct link): use window.location.origin instead of hardcoded 5chan.app
- Settings version link: use current origin
- FAQ: add 'Is 5chan just this website?' entry under Basics
- Remove pleb.bz from CHAN_5_HOSTNAMES

public/translations/zh/default.json

@@ -2,7 +2,7 @@
   "what_is_5chan": "5chan是什么?",
   "go": "去",
   "5chan_description": "5chan 是一个完全去中心化和开源的图像板，任何人都可以创建并以加密方式拥有无限数量的板块。板块所有者托管和审核其板块，并设置其 <1>Rules</1>。所有数据均为纯文本，且以点对点方式共享，包括嵌入图片的链接。查看 <2>FAQs</2> 了解更多。欢迎点击下方任意感兴趣的板块，立即开始！",
-  "no_global_rules_info": "您始终可以连接到任何论坛，完全P2P，没有人能阻止您。只需将其地址粘贴到上面的搜索字段中即可。",
+  "no_global_rules_info": "5chan 是无服务器应用，本网站只是打开它的方式之一。为避免依赖网站可用性，请<1>下载发行版</1>。",
   "boards": "论坛",
   "popular_threads": "热门主题",
   "options": "选项",