feat: improve squad management UX — rename, swap icons, color gift button

1. Rename "Управление серверами" → "Управление сквадами" across all
   4 locales (ru, en, zh, fa) — title, subtitle, nav, subscription
   options. The page manages RemnaWave squads, not individual servers.

2. Swap toggle button semantics — the button now shows the ACTION
   that will happen on click, not the current state:
   - Active squad: red X icon (click to deactivate)
   - Inactive squad: green checkmark (click to activate)

3. Gift/trial button: amber/orange when functional (clearly clickable),
   gray when disabled. Previously always gray, making it look inactive
   even when it could be clicked.

src/locales/zh.json

@@ -386,8 +386,8 @@
       "unlimited": "无限制",
       "buyTrafficGb": "购买 {{gb}} GB",
       "buyUnlimited": "购买无限流量",
-      "manageServers": "服务器管理",
-      "manageServersTitle": "服务器管理"
+      "manageServers": "小队管理",
+      "manageServersTitle": "小队管理"
     },
     "serverManagement": {
       "statusLegend": "✅ — 已连接 • ➕ — 将添加（付费）• ➖ — 将断开",
@@ -924,7 +924,7 @@
       "apps": "应用",
       "wheel": "转盘",
       "tariffs": "套餐",
-      "servers": "服务器",
+      "servers": "小队",
       "broadcasts": "群发",
       "emailTemplates": "邮件模板",
       "paymentMethods": "支付方式",