fix(billing): improve quota handling and error reporting for pre-consume operations

relay/image_handler.go

@@ -123,16 +123,6 @@ func ImageHelper(c *gin.Context, info *relaycommon.RelayInfo) (newAPIError *type
 		imageN = *request.N
 	}
 
-	// n is handled via OtherRatio so it is applied exactly once in quota
-	// calculation (both price-based and ratio-based paths).
-	// Adaptors may have already set a more accurate count from the
-	// upstream response; only set the default when they haven't.
-	if info.PriceData.UsePrice { // only price model use N ratio
-		if !info.PriceData.HasOtherRatio("n") {
-			info.PriceData.AddOtherRatio("n", float64(imageN))
-		}
-	}
-
 	if usage.(*dto.Usage).TotalTokens == 0 {
 		usage.(*dto.Usage).TotalTokens = 1
 	}