New /panel/api-docs route with a one-page reference covering every
/panel/api/* endpoint (Auth, Inbounds, Server, Nodes, Custom Geo,
Backup) plus a Bearer-token primer that reads the current token and
exposes Show/Copy/Regenerate inline. Sidebar gets an API Docs entry
right after Xray; the menu label is shared via menu.apiDocs across all
13 locales.
