feat: replace panel proxy URL with outbound-based egress bridge

Instead of requiring a manual SOCKS5/HTTP URL, the panel now lets the
admin pick an Xray outbound from a dropdown (same UX as Geodata
Auto-Update). At runtime, injectPanelEgress appends a loopback SOCKS
inbound (tag: panel-egress) and prepends a routing rule so the panel's
own HTTP traffic — version checks, Telegram, normal geo-file updates —
is routed through the chosen outbound. Xray-native Geodata Auto-Update
is unaffected (it uses its own geodata.outbound inside Xray). Blackhole
outbounds are excluded from both picker dropdowns since routing any
download through one just drops it. Translations updated for all 13
locales.

internal/web/translation/zh-TW.json

@@ -938,8 +938,9 @@
       "panelUrlPathDesc": "必須以 '/' 開頭，以 '/' 結尾",
       "pageSize": "分頁大小",
       "pageSizeDesc": "定義入站表的頁面大小。設定 0 表示禁用",
-      "panelProxy": "面板網路代理",
-      "panelProxyDesc": "透過此代理路由面板自身的出站請求(geo 更新、Xray/面板版本檢查、Telegram),以繞過伺服器端對 GitHub/Telegram 的過濾。接受 socks5:// 或 http(s)://,如本地 Xray SOCKS 入站。留空表示直連。",
+      "panelOutbound": "面板流量出站",
+      "panelOutboundDesc": "透過此 Xray 出站路由面板自身的請求(面板/Xray 版本檢查與下載、Telegram、一般 geo 檔案更新),以繞過伺服器端對 GitHub/Telegram 的過濾。本地橋接入站會自動加入執行中的設定並即時生效。Xray 原生的 Geodata 自動更新不受影響,它有自己的下載出站。留空表示直連。",
+      "panelOutboundPh": "直連",
       "remarkModel": "備註模型和分隔符",
       "datepicker": "日期選擇器",
       "datepickerPlaceholder": "選擇日期",