fix(i18n): rename subscription.servers object to subscription.serverManagement

Resolves conflict where subscription.servers existed as both a nested
object (for server management UI keys) and a pluralization base key.
Renamed the nested object to serverManagement in all 4 locales and
updated all t() references in Subscription.tsx.

src/locales/en.json

@@ -333,7 +333,7 @@
       "manageServers": "Server management",
       "manageServersTitle": "Server management"
     },
-    "servers": {
+    "serverManagement": {
       "statusLegend": "✅ — connected • ➕ — will be added (paid) • ➖ — will be disconnected",
       "discountBanner": "Your server discount: -{{percent}}%",
       "forDays": "(for {{days}} days)",

src/locales/fa.json

@@ -242,7 +242,7 @@
       "manageServers": "مدیریت سرورها",
       "manageServersTitle": "مدیریت سرورها"
     },
-    "servers": {
+    "serverManagement": {
       "statusLegend": "✅ — متصل • ➕ — اضافه خواهد شد (پولی) • ➖ — قطع خواهد شد",
       "discountBanner": "تخفیف سرور شما: -{{percent}}%",
       "forDays": "(برای {{days}} روز)",

src/locales/ru.json

@@ -355,7 +355,7 @@
       "manageServers": "Управление серверами",
       "manageServersTitle": "Управление серверами"
     },
-    "servers": {
+    "serverManagement": {
       "statusLegend": "✅ — подключено • ➕ — будет добавлено (платно) • ➖ — будет отключено",
       "discountBanner": "Ваша скидка на серверы: -{{percent}}%",
       "forDays": "(за {{days}} дн.)",

src/locales/zh.json

@@ -242,7 +242,7 @@
       "manageServers": "服务器管理",
       "manageServersTitle": "服务器管理"
     },
-    "servers": {
+    "serverManagement": {
       "statusLegend": "✅ — 已连接 • ➕ — 将添加（付费）• ➖ — 将断开",
       "discountBanner": "您的服务器折扣：-{{percent}}%",
       "forDays": "（{{days}} 天）",