feat: add OpenAI image generation controls

backend/internal/service/pricing_service.go

@@ -625,6 +625,9 @@ func normalizeModelNameForPricing(model string) string {
 	}
 
 	model = strings.TrimLeft(model, "/")
+	if canonical := canonicalizeOpenAIModelAliasSpelling(model); canonical != "" {
+		return canonical
+	}
 	return model
 }