feat(outbound): batched connection tester with direct timed HTTP probes

Replace the per-outbound burstObservatory polling (one temp xray spawn +
up to 15s of /debug/vars polling per outbound, serialised) with one
shared temp xray instance per batch: every tested outbound gets its own
loopback SOCKS inbound plus an inboundTag->outboundTag routing rule, and
the panel times a real HTTP request through each one in parallel. The
probe returns as soon as the response lands and records the HTTP status
plus an httptrace breakdown (proxy connect / TLS via outbound / first
byte) shown in the result popover.

New POST /panel/api/xray/testOutbounds endpoint (array in, results in
input order, max 50); the legacy /testOutbound endpoint now delegates to
the same engine. Test All chunks HTTP probes 16 per request, and a batch
whose shared process never comes up (one structurally-broken outbound
poisons the config) retries each item in an isolated instance so the
broken outbound reports xray's real error while the rest still test.

internal/web/translation/ar-EG.json

@@ -1384,6 +1384,10 @@
         "testError": "فشل اختبار المخرج",
         "testModeTooltip": "TCP: فحص dial سريع. HTTP: طلب كامل عبر xray.",
         "testAll": "اختبار الكل",
+        "httpStatus": "حالة HTTP",
+        "breakdownConnect": "اتصال البروكسي",
+        "breakdownTls": "TLS عبر الصادر",
+        "breakdownTtfb": "أول بايت",
         "nordvpn": "NordVPN",
         "accessToken": "رمز الوصول",
         "country": "الدولة",

internal/web/translation/en-US.json

@@ -1387,6 +1387,10 @@
         "testError": "Failed to test outbound",
         "testModeTooltip": "TCP: fast dial-only probe. HTTP: full request through xray.",
         "testAll": "Test all",
+        "httpStatus": "HTTP status",
+        "breakdownConnect": "Proxy connect",
+        "breakdownTls": "TLS via outbound",
+        "breakdownTtfb": "First byte",
         "nordvpn": "NordVPN",
         "accessToken": "Access Token",
         "country": "Country",

internal/web/translation/es-ES.json

@@ -1384,6 +1384,10 @@
         "testError": "Error al probar la salida",
         "testModeTooltip": "TCP: sonda rápida solo de dial. HTTP: petición completa a través de xray.",
         "testAll": "Probar todo",
+        "httpStatus": "Estado HTTP",
+        "breakdownConnect": "Conexión al proxy",
+        "breakdownTls": "TLS vía salida",
+        "breakdownTtfb": "Primer byte",
         "nordvpn": "NordVPN",
         "accessToken": "Token de acceso",
         "country": "País",

internal/web/translation/fa-IR.json

@@ -1384,6 +1384,10 @@
         "testError": "خطا در تست خروجی",
         "testModeTooltip": "TCP: فقط dial سریع. HTTP: درخواست کامل از طریق xray.",
         "testAll": "تست همه",
+        "httpStatus": "وضعیت HTTP",
+        "breakdownConnect": "اتصال پروکسی",
+        "breakdownTls": "TLS از طریق خروجی",
+        "breakdownTtfb": "اولین بایت",
         "nordvpn": "NordVPN",
         "accessToken": "توکن دسترسی",
         "country": "کشور",

internal/web/translation/id-ID.json

@@ -1384,6 +1384,10 @@
         "testError": "Gagal menguji outbound",
         "testModeTooltip": "TCP: probe dial-only cepat. HTTP: permintaan penuh via xray.",
         "testAll": "Tes semua",
+        "httpStatus": "Status HTTP",
+        "breakdownConnect": "Koneksi proxy",
+        "breakdownTls": "TLS melalui outbound",
+        "breakdownTtfb": "Byte pertama",
         "nordvpn": "NordVPN",
         "accessToken": "Token Akses",
         "country": "Negara",

internal/web/translation/ja-JP.json

@@ -1384,6 +1384,10 @@
         "testError": "アウトバウンドのテストに失敗しました",
         "testModeTooltip": "TCP: 高速 dial-only プローブ。HTTP: xray を経由した完全リクエスト。",
         "testAll": "すべてテスト",
+        "httpStatus": "HTTPステータス",
+        "breakdownConnect": "プロキシ接続",
+        "breakdownTls": "アウトバウンド経由のTLS",
+        "breakdownTtfb": "最初のバイト",
         "nordvpn": "NordVPN",
         "accessToken": "アクセストークン",
         "country": "国",

internal/web/translation/pt-BR.json

@@ -1384,6 +1384,10 @@
         "testError": "Falha ao testar saída",
         "testModeTooltip": "TCP: sondagem rápida apenas de dial. HTTP: requisição completa pelo xray.",
         "testAll": "Testar todos",
+        "httpStatus": "Status HTTP",
+        "breakdownConnect": "Conexão do proxy",
+        "breakdownTls": "TLS via saída",
+        "breakdownTtfb": "Primeiro byte",
         "nordvpn": "NordVPN",
         "accessToken": "Token de Acesso",
         "country": "País",

internal/web/translation/ru-RU.json

@@ -1384,6 +1384,10 @@
         "testError": "Не удалось протестировать исходящее подключение",
         "testModeTooltip": "TCP: быстрый dial-only probe. HTTP: полный запрос через xray.",
         "testAll": "Тестировать все",
+        "httpStatus": "HTTP-статус",
+        "breakdownConnect": "Подключение к прокси",
+        "breakdownTls": "TLS через исходящий",
+        "breakdownTtfb": "Первый байт",
         "nordvpn": "NordVPN",
         "accessToken": "Токен доступа",
         "country": "Страна",

internal/web/translation/tr-TR.json

@@ -1385,6 +1385,10 @@
         "testError": "Giden bağlantı test edilemedi",
         "testModeTooltip": "TCP: hızlı sadece arama (dial-only) testi. HTTP: Xray üzerinden tam istek.",
         "testAll": "Tümünü Test Et",
+        "httpStatus": "HTTP durumu",
+        "breakdownConnect": "Proxy bağlantısı",
+        "breakdownTls": "Giden üzerinden TLS",
+        "breakdownTtfb": "İlk bayt",
         "nordvpn": "NordVPN",
         "accessToken": "Erişim Jetonu",
         "country": "Ülke",

internal/web/translation/uk-UA.json

@@ -1384,6 +1384,10 @@
         "testError": "Не вдалося протестувати вихідне з'єднання",
         "testModeTooltip": "TCP: швидкий dial-only probe. HTTP: повний запит через xray.",
         "testAll": "Тестувати всі",
+        "httpStatus": "HTTP-статус",
+        "breakdownConnect": "Підключення до проксі",
+        "breakdownTls": "TLS через вихідний",
+        "breakdownTtfb": "Перший байт",
         "nordvpn": "NordVPN",
         "accessToken": "Токен доступу",
         "country": "Країна",

internal/web/translation/vi-VN.json

@@ -1384,6 +1384,10 @@
         "testError": "Không thể kiểm tra đầu ra",
         "testModeTooltip": "TCP: probe dial nhanh. HTTP: yêu cầu đầy đủ qua xray.",
         "testAll": "Kiểm tra tất cả",
+        "httpStatus": "Trạng thái HTTP",
+        "breakdownConnect": "Kết nối proxy",
+        "breakdownTls": "TLS qua outbound",
+        "breakdownTtfb": "Byte đầu tiên",
         "nordvpn": "NordVPN",
         "accessToken": "Mã truy cập",
         "country": "Quốc gia",

internal/web/translation/zh-CN.json

@@ -1384,6 +1384,10 @@
         "testError": "测试出站失败",
         "testModeTooltip": "TCP: 快速 dial-only 探测。HTTP: 通过 xray 的完整请求。",
         "testAll": "全部测试",
+        "httpStatus": "HTTP 状态",
+        "breakdownConnect": "代理连接",
+        "breakdownTls": "经由出站的 TLS",
+        "breakdownTtfb": "首字节",
         "nordvpn": "NordVPN",
         "accessToken": "访问令牌",
         "country": "国家",

internal/web/translation/zh-TW.json

@@ -1384,6 +1384,10 @@
         "testError": "測試出站失敗",
         "testModeTooltip": "TCP: 快速 dial-only 探測。HTTP: 透過 xray 的完整請求。",
         "testAll": "全部測試",
+        "httpStatus": "HTTP 狀態",
+        "breakdownConnect": "代理連線",
+        "breakdownTls": "經由出站的 TLS",
+        "breakdownTtfb": "首位元組",
         "nordvpn": "NordVPN",
         "accessToken": "訪問令牌",
         "country": "國家",