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/en-US/system.json

@@ -3,6 +3,7 @@
   "common": {
     "cancel": "Cancel",
     "save": "Save Settings",
+    "saving": "Saving...",
     "saveFailed": "Save Failed",
     "saveSuccess": "Save Successful"
   },
@@ -23,6 +24,10 @@
     "description": "Configure user invitation and referral reward settings",
     "forcedInvite": "Require Invitation to Register",
     "forcedInviteDescription": "When enabled, users must register through an invitation link",
+    "giftDays": "Invite Gift Days",
+    "giftDaysDescription": "When referral percentage is 0, both the inviter and invitee receive this many extra subscription days after the invitee makes a purchase",
+    "giftDaysPlaceholder": "Enter days",
+    "giftDaysSuffix": "day(s)",
     "inputPlaceholder": "Please enter",
     "onlyFirstPurchase": "First Purchase Reward Only",
     "onlyFirstPurchaseDescription": "When enabled, referrers only receive rewards for the first purchase by referred users",
@@ -42,6 +47,22 @@
     "title": "Log Cleanup Settings"
   },
   "logSettings": "Log Settings",
+  "signature": {
+    "title": "Request Signature",
+    "description": "Enable or disable request signature verification for public APIs",
+    "enable": "Enable Signature Verification",
+    "enableDescription": "When enabled, clients can trigger strict signature verification by sending X-Signature-Enabled: 1",
+    "saveSuccess": "Save Successful",
+    "saveFailed": "Save Failed"
+  },
+  "subscribeMode": {
+    "title": "Subscription Mode",
+    "description": "Configure single or multiple subscription purchase behavior",
+    "singleSubscriptionMode": "Single Subscription Mode",
+    "singleSubscriptionModeDescription": "After enabling, users can only purchase/renew one subscription in the same account",
+    "saveSuccess": "Subscription mode updated successfully",
+    "saveFailed": "Failed to update settings"
+  },
   "privacyPolicy": {
     "description": "Edit and manage privacy policy content",
     "title": "Privacy Policy"