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/round.go

@@ -1,24 +1,14 @@
 package billingexpr
 
-import "math"
+import "github.com/QuantumNous/new-api/common"
 
 // QuotaRound converts a float64 quota value to int using half-away-from-zero
-// rounding. Every tiered billing path (pre-consume, settlement, breakdown
-// validation, log fields) MUST use this function to avoid +-1 discrepancies.
+// rounding with int32 saturation. Every tiered billing path (pre-consume,
+// settlement, breakdown validation, log fields) MUST use this function to
+// avoid +-1 discrepancies.
 //
-// The result saturates at int32 bounds: quota columns are 32-bit integers in
-// the database, and an oversized expression result must never wrap around
-// and turn a charge into a credit.
+// It delegates to common.QuotaRound so all quota rounding/conversion shares
+// one saturation + logging policy (see common/quota_math.go).
 func QuotaRound(f float64) int {
-	r := math.Round(f)
-	if math.IsNaN(r) {
-		return 0
-	}
-	if r >= math.MaxInt32 {
-		return math.MaxInt32
-	}
-	if r <= math.MinInt32 {
-		return math.MinInt32
-	}
-	return int(r)
+	return common.QuotaRound(f)
 }