feat(settings): panel network proxy for the panel's own outbound requests

Add a panelProxy setting that routes the panel's self-initiated HTTP requests (geo updates, Xray version/core download, panel update check) through an admin-configured socks5/http(s) proxy, to bypass server-side filtering of GitHub/Telegram. The Telegram bot falls back to it when tgBotProxy is empty (socks5 only). New util/netproxy.NewHTTPClient builds the proxied client.

Also fix the Mixed-inbound SOCKS/HTTP share URLs that had host:port and user:pass in the wrong order, and consolidate the Telegram settings tab (move API server into the general tab, drop the empty Proxy & Server tab).

web/translation/en-US.json

@@ -686,6 +686,8 @@
       "panelUrlPathDesc": "The URI path for the web panel. (begins with ‘/‘ and concludes with ‘/‘)",
       "pageSize": "Pagination Size",
       "pageSizeDesc": "Define page size for inbounds table. (0 = disable)",
+      "panelProxy": "Panel Network Proxy",
+      "panelProxyDesc": "Routes the panel's own outbound requests (geo updates, Xray/panel version checks, Telegram) through this proxy to bypass server-side filtering of GitHub/Telegram. Accepts socks5:// or http(s)://, e.g. a local Xray SOCKS inbound. Leave empty for a direct connection.",
       "remarkModel": "Remark Model & Separation Character",
       "datepicker": "Calendar Type",
       "datepickerPlaceholder": "Select date",

web/translation/fa-IR.json

@@ -621,6 +621,8 @@
       "panelUrlPathDesc": "برای وب پنل. با '/' شروع‌ و با '/' خاتمه‌ می‌یابد URI مسیر",
       "pageSize": "اندازه صفحه بندی جدول",
       "pageSizeDesc": "(اندازه صفحه برای جدول ورودی‌ها.(0 = غیرفعال",
+      "panelProxy": "پراکسی شبکه‌ی پنل",
+      "panelProxyDesc": "درخواست‌های خروجیِ خودِ پنل (آپدیت geo، چک نسخه‌ی Xray و پنل، تلگرام) را از این پراکسی عبور می‌دهد تا فیلترینگ سروری گیت‌هاب/تلگرام دور زده شود. پشتیبانی از socks5:// و http(s)://، برای نمونه یک اینباند SOCKS لوکالِ Xray. برای اتصال مستقیم خالی بگذارید.",
       "remarkModel": "نام‌کانفیگ و جداکننده",
       "datepicker": "نوع تقویم",
       "datepickerPlaceholder": "انتخاب تاریخ",