✨ chore: Improve subscription billing fallback and UI states

Add a lightweight active-subscription check to skip subscription pre-consume when none exist, reducing unnecessary transactions and locks. In the subscription UI, disable subscription-first options when no active plan is available, show the effective fallback to wallet with a clear notice, and distinguish “invalidated” from “expired” states. Update i18n strings across supported locales to reflect the new messages and status labels.

web/src/i18n/locales/en.json

@@ -2729,10 +2729,13 @@
     "我的订阅": "My Subscriptions",
     "个生效中": "active",
     "无生效": "No active",
+    "已保存偏好为": "Saved preference: ",
+    "，当前无生效订阅，将自动使用钱包": ", no active subscription. Wallet will be used automatically.",
     "个已过期": "expired",
     "订阅": "Subscription",
     "至": "until",
     "过期于": "Expires at",
+    "作废于": "Invalidated at",
     "购买套餐后即可享受模型权益": "Enjoy model benefits after purchasing a plan",
     "限购": "Limit",
     "推荐": "Recommended",