✨ 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.

service/billing_session.go

@@ -323,6 +323,13 @@ func NewBillingSession(c *gin.Context, relayInfo *relaycommon.RelayInfo, preCons
 	case "subscription_first":
 		fallthrough
 	default:
+		hasSub, err := model.HasActiveUserSubscription(relayInfo.UserId)
+		if err != nil {
+			return nil, types.NewError(err, types.ErrorCodeQueryDataError, types.ErrOptionWithSkipRetry())
+		}
+		if !hasSub {
+			return tryWallet()
+		}
 		session, err := trySubscription()
 		if err != nil {
 			if err.GetErrorCode() == types.ErrorCodeInsufficientUserQuota {