feat: 自定义版本功能更新

- 新增家庭共享订阅管理
- 新增用户邀请统计
- 新增签名和订阅模式设置表单
- 更新 API 服务层和国际化文件
- UI 组件优化（enhanced-input、pro-table）

apps/admin/public/assets/locales/zh-CN/system.json

@@ -3,6 +3,7 @@
   "common": {
     "cancel": "取消",
     "save": "保存设置",
+    "saving": "保存中...",
     "saveFailed": "保存失败",
     "saveSuccess": "保存成功"
   },
@@ -23,6 +24,10 @@
     "description": "配置用户邀请和推荐奖励设置",
     "forcedInvite": "强制邀请注册",
     "forcedInviteDescription": "启用后，用户必须通过邀请链接注册",
+    "giftDays": "邀请赠送天数",
+    "giftDaysDescription": "当推荐佣金比例为 0 时，被邀请人完成购买后，邀请人和被邀请人各自获得的订阅延长天数",
+    "giftDaysPlaceholder": "请输入天数",
+    "giftDaysSuffix": "天",
     "inputPlaceholder": "请输入",
     "onlyFirstPurchase": "仅首次购买奖励",
     "onlyFirstPurchaseDescription": "启用后，推荐人仅在被推荐用户首次购买时获得奖励",
@@ -42,6 +47,22 @@
     "title": "日志清理设置"
   },
   "logSettings": "日志设置",
+  "signature": {
+    "title": "请求签名",
+    "description": "启用或禁用公共 API 的请求签名验证",
+    "enable": "启用签名验证",
+    "enableDescription": "启用后，客户端可以通过发送 X-Signature-Enabled: 1 来触发严格的签名验证",
+    "saveSuccess": "保存成功",
+    "saveFailed": "保存失败"
+  },
+  "subscribeMode": {
+    "title": "订阅模式",
+    "description": "配置单订阅或多订阅购买行为",
+    "singleSubscriptionMode": "单订阅模式",
+    "singleSubscriptionModeDescription": "启用后，用户在同一账户中只能购买/续费一个订阅",
+    "saveSuccess": "订阅模式更新成功",
+    "saveFailed": "更新设置失败"
+  },
   "privacyPolicy": {
     "description": "编辑和管理隐私政策内容",
     "title": "隐私政策"