fix(billing): surface quota saturation events for admin auditing

Thread int32 saturation clamps from tiered settlement and video task
recompute into the consume/task logs under admin_info, so oversized or
malformed billing inputs stay auditable. Clamp negative audio duration
before token conversion and gate the saturation UI markers on admin.

pkg/billingexpr/settle.go

@@ -1,5 +1,7 @@
 package billingexpr
 
+import "github.com/QuantumNous/new-api/common"
+
 // quotaConversion converts raw expression output to quota based on the
 // expression version. This is the central dispatch point for future versions
 // that may use a different conversion formula.
@@ -23,7 +25,7 @@ func ComputeTieredQuotaWithRequest(snap *BillingSnapshot, params TokenParams, re
 	}
 
 	quotaBeforeGroup := quotaConversion(cost, snap)
-	afterGroup := QuotaRound(quotaBeforeGroup * snap.GroupRatio)
+	afterGroup, clamp := common.QuotaRoundChecked(quotaBeforeGroup * snap.GroupRatio)
 	crossed := trace.MatchedTier != snap.EstimatedTier
 
 	return TieredResult{
@@ -31,5 +33,6 @@ func ComputeTieredQuotaWithRequest(snap *BillingSnapshot, params TokenParams, re
 		ActualQuotaAfterGroup:  afterGroup,
 		MatchedTier:            trace.MatchedTier,
 		CrossedTier:            crossed,
+		Clamp:                  clamp,
 	}, nil
 }