feat: add Referrals tab to admin user detail page

- New Рефералы tab with three sections:
  - Referred By: shows who referred this user, assign/remove referrer
  - Stats grid: total referrals, earnings, commission, referral code
  - Referrals list: all referred users with navigate and remove buttons
- User search with debounce for assigning referrer
- Shows warning when selected user already has a referrer
- API methods: assignReferrer, removeReferrer, removeReferral
- i18n translations for all 4 locales (en, ru, zh, fa)

src/locales/en.json

@@ -2940,7 +2940,8 @@
           "balance": "Balance",
           "sync": "Synchronization",
           "tickets": "Tickets",
-          "gifts": "Gifts"
+          "gifts": "Gifts",
+          "referrals": "Referrals"
         },
         "noTickets": "No tickets from this user",
         "ticketsCount": "tickets",
@@ -3100,6 +3101,26 @@
           "unknownUser": "Unknown",
           "totalSent": "Total sent",
           "totalReceived": "Total received"
+        },
+        "referrals": {
+          "referredBy": "Referred By",
+          "noReferrer": "No referrer assigned",
+          "assignReferrer": "Assign Referrer",
+          "removeReferrer": "Remove",
+          "referrerAssigned": "Referrer assigned successfully",
+          "referrerRemoved": "Referrer removed successfully",
+          "totalReferrals": "Total Referrals",
+          "totalEarnings": "Total Earnings",
+          "commission": "Commission",
+          "referralCode": "Referral Code",
+          "default": "default",
+          "referralsList": "Referrals",
+          "noReferrals": "No referrals yet",
+          "removeReferral": "Remove referral",
+          "referralRemoved": "Referral removed successfully",
+          "searchPlaceholder": "Search by name, email, or Telegram ID...",
+          "alreadyReferred": "already has referrer",
+          "noUsersFound": "No users found"
         }
       }
     },

src/locales/fa.json

@@ -2562,7 +2562,8 @@
           "balance": "موجودی",
           "sync": "همگام‌سازی",
           "tickets": "تیکت‌ها",
-          "gifts": "هدایا"
+          "gifts": "هدایا",
+          "referrals": "معرفی‌ها"
         },
         "noTickets": "این کاربر تیکتی ندارد",
         "ticketsCount": "تیکت",
@@ -2718,6 +2719,26 @@
           "unknownUser": "ناشناس",
           "totalSent": "کل ارسال شده",
           "totalReceived": "کل دریافت شده"
+        },
+        "referrals": {
+          "referredBy": "معرفی‌شده توسط",
+          "noReferrer": "معرفی‌کننده‌ای تعیین نشده",
+          "assignReferrer": "تعیین معرفی‌کننده",
+          "removeReferrer": "حذف",
+          "referrerAssigned": "معرفی‌کننده تعیین شد",
+          "referrerRemoved": "معرفی‌کننده حذف شد",
+          "totalReferrals": "کل معرفی‌ها",
+          "totalEarnings": "کل درآمد",
+          "commission": "کمیسیون",
+          "referralCode": "کد معرفی",
+          "default": "پیش‌فرض",
+          "referralsList": "لیست معرفی‌ها",
+          "noReferrals": "هنوز معرفی‌ای نیست",
+          "removeReferral": "حذف معرفی",
+          "referralRemoved": "معرفی حذف شد",
+          "searchPlaceholder": "جستجو بر اساس نام، ایمیل یا شناسه تلگرام...",
+          "alreadyReferred": "قبلاً معرفی شده",
+          "noUsersFound": "کاربری یافت نشد"
         }
       }
     },

src/locales/ru.json

@@ -3452,7 +3452,8 @@
           "balance": "Баланс",
           "sync": "Синхронизация",
           "tickets": "Тикеты",
-          "gifts": "Подарки"
+          "gifts": "Подарки",
+          "referrals": "Рефералы"
         },
         "noTickets": "У пользователя нет тикетов",
         "ticketsCount": "тикетов",
@@ -3611,6 +3612,26 @@
           "unknownUser": "Неизвестный",
           "totalSent": "Всего отправлено",
           "totalReceived": "Всего получено"
+        },
+        "referrals": {
+          "referredBy": "Приглашён",
+          "noReferrer": "Реферер не назначен",
+          "assignReferrer": "Назначить реферера",
+          "removeReferrer": "Удалить",
+          "referrerAssigned": "Реферер назначен",
+          "referrerRemoved": "Реферер удалён",
+          "totalReferrals": "Всего рефералов",
+          "totalEarnings": "Всего заработано",
+          "commission": "Комиссия",
+          "referralCode": "Реферальный код",
+          "default": "стандарт",
+          "referralsList": "Рефералы",
+          "noReferrals": "Рефералов пока нет",
+          "removeReferral": "Удалить реферала",
+          "referralRemoved": "Реферал удалён",
+          "searchPlaceholder": "Поиск по имени, email или Telegram ID...",
+          "alreadyReferred": "уже чей-то реферал",
+          "noUsersFound": "Пользователи не найдены"
         }
       }
     },

src/locales/zh.json

@@ -2561,7 +2561,8 @@
           "balance": "余额",
           "sync": "同步",
           "tickets": "工单",
-          "gifts": "礼物"
+          "gifts": "礼物",
+          "referrals": "推荐"
         },
         "noTickets": "该用户没有工单",
         "ticketsCount": "个工单",
@@ -2717,6 +2718,26 @@
           "unknownUser": "未知",
           "totalSent": "已发送总数",
           "totalReceived": "已收到总数"
+        },
+        "referrals": {
+          "referredBy": "推荐人",
+          "noReferrer": "未分配推荐人",
+          "assignReferrer": "分配推荐人",
+          "removeReferrer": "移除",
+          "referrerAssigned": "推荐人已分配",
+          "referrerRemoved": "推荐人已移除",
+          "totalReferrals": "总推荐数",
+          "totalEarnings": "总收益",
+          "commission": "佣金",
+          "referralCode": "推荐码",
+          "default": "默认",
+          "referralsList": "推荐列表",
+          "noReferrals": "暂无推荐",
+          "removeReferral": "移除推荐",
+          "referralRemoved": "推荐已移除",
+          "searchPlaceholder": "按名称、邮箱或 Telegram ID 搜索...",
+          "alreadyReferred": "已有推荐人",
+          "noUsersFound": "未找到用户"
         }
       }
     },