feat: sync latest openai speech struct

https://platform.openai.com/docs/api-reference/audio/createSpeech

dto/audio.go

@@ -10,8 +10,10 @@ type AudioRequest struct {
 	Model          string  `json:"model"`
 	Input          string  `json:"input"`
 	Voice          string  `json:"voice"`
-	Speed          float64 `json:"speed,omitempty"`
+	Instructions   string  `json:"instructions,omitempty"`
 	ResponseFormat string  `json:"response_format,omitempty"`
+	Speed          float64 `json:"speed,omitempty"`
+	StreamFormat   string  `json:"stream_format,omitempty"`
 }
 
 func (r *AudioRequest) GetTokenCountMeta() *types.TokenCountMeta {