feat(fallbacks): add per-rule dest override

Operators can now type an explicit dest (e.g. "8443", "127.0.0.1:8443",
"/dev/shm/x.sock") on each fallback row to override the auto-resolved
child listen+port. Empty keeps the existing auto behavior.

Adds the column to inbound_fallbacks (GORM AutoMigrate), threads it
through the panel form, API docs, and translations.

web/translation/ar-EG.json

@@ -266,6 +266,7 @@
         "add": "إضافة fallback",
         "pickInbound": "اختر inbound",
         "matchAny": "أي",
+        "destPlaceholder": "تلقائي (listen:port للفرع)",
         "rederive": "إعادة الملء من الفرع",
         "rederived": "تم إعادة الملء من الفرع",
         "editAdvanced": "تحرير حقول التوجيه",

web/translation/en-US.json

@@ -266,6 +266,7 @@
         "add": "Add fallback",
         "pickInbound": "Pick an inbound",
         "matchAny": "any",
+        "destPlaceholder": "auto (child listen:port)",
         "rederive": "Re-fill from child",
         "rederived": "Re-filled from child",
         "editAdvanced": "Edit routing fields",

web/translation/es-ES.json

@@ -266,6 +266,7 @@
         "add": "Añadir fallback",
         "pickInbound": "Selecciona un inbound",
         "matchAny": "cualquiera",
+        "destPlaceholder": "automático (listen:puerto del hijo)",
         "rederive": "Rellenar desde el hijo",
         "rederived": "Rellenado desde el hijo",
         "editAdvanced": "Editar campos de enrutamiento",

web/translation/fa-IR.json

@@ -266,6 +266,7 @@
         "add": "افزودن فال‌بک",
         "pickInbound": "یک اینباند انتخاب کنید",
         "matchAny": "همه",
+        "destPlaceholder": "خودکار (listen:port فرزند)",
         "rederive": "پر کردن مجدد از فرزند",
         "rederived": "از فرزند پر شد",
         "editAdvanced": "ویرایش فیلدهای مسیریابی",

web/translation/id-ID.json

@@ -266,6 +266,7 @@
         "add": "Tambah fallback",
         "pickInbound": "Pilih inbound",
         "matchAny": "apa pun",
+        "destPlaceholder": "otomatis (listen:port child)",
         "rederive": "Isi ulang dari child",
         "rederived": "Diisi ulang dari child",
         "editAdvanced": "Edit field routing",

web/translation/ja-JP.json

@@ -266,6 +266,7 @@
         "add": "フォールバックを追加",
         "pickInbound": "インバウンドを選択",
         "matchAny": "任意",
+        "destPlaceholder": "自動（子の listen:port）",
         "rederive": "子から再取得",
         "rederived": "子から再取得しました",
         "editAdvanced": "ルーティング項目を編集",

web/translation/pt-BR.json

@@ -266,6 +266,7 @@
         "add": "Adicionar fallback",
         "pickInbound": "Escolha um inbound",
         "matchAny": "qualquer",
+        "destPlaceholder": "automático (listen:porta do filho)",
         "rederive": "Preencher a partir do filho",
         "rederived": "Preenchido a partir do filho",
         "editAdvanced": "Editar campos de roteamento",

web/translation/ru-RU.json

@@ -266,6 +266,7 @@
         "add": "Добавить фолбэк",
         "pickInbound": "Выберите инбаунд",
         "matchAny": "любой",
+        "destPlaceholder": "авто (listen:порт дочернего)",
         "rederive": "Заполнить из дочернего",
         "rederived": "Заполнено из дочернего",
         "editAdvanced": "Изменить поля маршрутизации",

web/translation/tr-TR.json

@@ -266,6 +266,7 @@
         "add": "Fallback ekle",
         "pickInbound": "Bir inbound seç",
         "matchAny": "herhangi",
+        "destPlaceholder": "otomatik (child listen:port)",
         "rederive": "Child'dan yeniden doldur",
         "rederived": "Child'dan yeniden dolduruldu",
         "editAdvanced": "Yönlendirme alanlarını düzenle",

web/translation/uk-UA.json

@@ -266,6 +266,7 @@
         "add": "Додати фолбек",
         "pickInbound": "Оберіть інбаунд",
         "matchAny": "будь-який",
+        "destPlaceholder": "авто (listen:порт дочірнього)",
         "rederive": "Заповнити з дочірнього",
         "rederived": "Заповнено з дочірнього",
         "editAdvanced": "Редагувати поля маршрутизації",

web/translation/vi-VN.json

@@ -266,6 +266,7 @@
         "add": "Thêm fallback",
         "pickInbound": "Chọn một inbound",
         "matchAny": "bất kỳ",
+        "destPlaceholder": "tự động (listen:port của child)",
         "rederive": "Điền lại từ child",
         "rederived": "Đã điền lại từ child",
         "editAdvanced": "Sửa trường định tuyến",

web/translation/zh-CN.json

@@ -266,6 +266,7 @@
         "add": "添加回落",
         "pickInbound": "选择一个入站",
         "matchAny": "任意",
+        "destPlaceholder": "自动（子入站 listen:port）",
         "rederive": "从子入站重新填充",
         "rederived": "已从子入站重新填充",
         "editAdvanced": "编辑路由字段",

web/translation/zh-TW.json

@@ -266,6 +266,7 @@
         "add": "新增回落",
         "pickInbound": "選擇一個入站",
         "matchAny": "任何",
+        "destPlaceholder": "自動（子入站 listen:port）",
         "rederive": "從子入站重新填入",
         "rederived": "已從子入站重新填入",
         "editAdvanced": "編輯路由欄位",