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/en.json

@@ -555,8 +555,8 @@
       "unlimited": "Unlimited",
       "buyTrafficGb": "Buy {{gb}} GB",
       "buyUnlimited": "Buy Unlimited",
-      "manageServers": "Server management",
-      "manageServersTitle": "Server management"
+      "manageServers": "Squad management",
+      "manageServersTitle": "Squad management"
     },
     "serverManagement": {
       "statusLegend": "✅ — connected • ➕ — will be added (paid) • ➖ — will be disconnected",
@@ -1100,7 +1100,7 @@
       "apps": "Apps",
       "wheel": "Wheel",
       "tariffs": "Tariffs",
-      "servers": "Servers",
+      "servers": "Squads",
       "banSystem": "Ban Monitoring",
       "broadcasts": "Broadcasts",
       "users": "Users",
@@ -2351,8 +2351,8 @@
       }
     },
     "servers": {
-      "title": "Server Management",
-      "subtitle": "Configure VPN servers",
+      "title": "Squad Management",
+      "subtitle": "Configure squads",
       "sync": "Sync",
       "syncing": "Syncing...",
       "syncNow": "Sync now",