feat(panel): in-panel API documentation page

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.

web/translation/fa-IR.json

@@ -97,6 +97,7 @@
     "nodes": "نودها",
     "settings": "تنظیمات پنل",
     "xray": "پیکربندی ایکس‌ری",
+    "apiDocs": "API Docs",
     "logout": "خروج",
     "link": "مدیریت"
   },