Add multi-server 3x-ui registry with per-panel subscription URLs.

Admins can manage several 3x-ui panels by name and select which one issues invite/user configs via that server's /sub base URL.

Co-authored-by: Cursor <cursoragent@cursor.com>

translations/en.json

@@ -302,6 +302,16 @@
   "xui_inbound_label": "VLESS inbound",
   "xui_inbound_auto": "Auto (first VLESS inbound)",
   "xui_inbound_hint": "Used when creating 3x-ui VLESS configs. Create a VLESS inbound in 3x-ui first.",
+  "xui_servers_title": "3x-ui servers",
+  "xui_servers_hint": "Add multiple 3x-ui panels. When creating invites/configs, pick a server by name — its subscription base URL is used.",
+  "xui_servers_empty": "No 3x-ui servers yet. Click Add server.",
+  "xui_servers_manage_hint": "Panel URLs and subscription bases are managed in the “3x-ui servers” section below.",
+  "xui_server_add": "Add server",
+  "xui_server_name_label": "Name / description",
+  "xui_server_name_hint": "Shown in invites and user forms (e.g. US, NL, Home).",
+  "xui_server_select_label": "3x-ui server",
+  "xui_server_select_hint": "Choose which 3x-ui panel (by description) will issue the subscription URL.",
+  "xui_server_delete_confirm": "Delete this 3x-ui server from the panel?",
   "sync_now_btn": "🔄 Sync now",
   "delete_sync_btn": "🗑 Delete synchronization",
   "auto_create_conns": "Create connections automatically",