feat: add subscription selector to admin sync tab for multi-tariff

- Add subscription dropdown to sync tab when user has 2+ subscriptions
- Pass subscription_id to getSyncStatus, syncFromPanel, syncToPanel
- loadSyncStatus re-fetches when selected subscription changes
- Show tariff name in UUID info section from API response
- Add selectSubscription i18n keys to all 4 locales

src/locales/zh.json

@@ -2577,6 +2577,7 @@
           "recentTransactions": "最近交易"
         },
         "sync": {
+          "selectSubscription": "选择订阅",
           "hasDifferences": "存在差异",
           "synced": "已同步",
           "bot": "机器人",