feat: 新增音频格式与采样率配置，完善OpenAI兼容格式映射

1.  新增BYTEDANCE_TTS_FORMAT和BYTEDANCE_TTS_SAMPLE_RATE环境变量配置
2.  实现OpenAI TTS格式到火山API格式的映射转换
3.  自动处理wav格式：内部用pcm请求后封装标准WAV头
4.  动态设置响应Content-Type，适配不同输出格式
5.  更新文档与配置示例，完善日志与错误处理

setting/config.go

@@ -50,6 +50,26 @@ func InitTTSConfig() error {
 		}
 	}
 
+	// 音频格式，默认 mp3（文档默认值，流式场景下 wav 会多次返回 header，不推荐）
+	format := os.Getenv("BYTEDANCE_TTS_FORMAT")
+	if format == "" {
+		format = "mp3"
+	}
+
+	// 采样率，默认 24000
+	sampleRate := 24000
+	if srStr := os.Getenv("BYTEDANCE_TTS_SAMPLE_RATE"); srStr != "" {
+		if sr, err := fmt.Sscanf(srStr, "%d", &sampleRate); err != nil || sr != 1 {
+			log.Printf("无效的采样率设置 '%s'，使用默认值: 24000", srStr)
+			sampleRate = 24000
+		}
+		validRates := map[int]bool{8000: true, 16000: true, 22050: true, 24000: true, 32000: true, 44100: true, 48000: true}
+		if !validRates[sampleRate] {
+			log.Printf("不支持的采样率 %d，使用默认值: 24000", sampleRate)
+			sampleRate = 24000
+		}
+	}
+
 	TTSConfig = dto.ByteDanceTTSConfig{
 		ApiKey:     apiKey,
 		ResourceId: resourceId,
@@ -57,6 +77,8 @@ func InitTTSConfig() error {
 		Model:      model,
 		URL:        url,
 		Timeout:    timeout,
+		Format:     format,
+		SampleRate: sampleRate,
 	}
 	return nil
 }
@@ -76,11 +98,13 @@ func CheckEnvironmentVariables() map[string]interface{} {
 	}
 
 	optionalVars := map[string]bool{
-		"BYTEDANCE_TTS_TIMEOUT": os.Getenv("BYTEDANCE_TTS_TIMEOUT") != "",
-		"BYTEDANCE_TTS_MODEL":   os.Getenv("BYTEDANCE_TTS_MODEL") != "",
-		"OPENAI_TTS_API_KEY":    os.Getenv("OPENAI_TTS_API_KEY") != "",
-		"ALLOWED_ORIGINS":       os.Getenv("ALLOWED_ORIGINS") != "",
-		"PORT":                  os.Getenv("PORT") != "",
+		"BYTEDANCE_TTS_TIMEOUT":     os.Getenv("BYTEDANCE_TTS_TIMEOUT") != "",
+		"BYTEDANCE_TTS_MODEL":       os.Getenv("BYTEDANCE_TTS_MODEL") != "",
+		"BYTEDANCE_TTS_FORMAT":      os.Getenv("BYTEDANCE_TTS_FORMAT") != "",
+		"BYTEDANCE_TTS_SAMPLE_RATE": os.Getenv("BYTEDANCE_TTS_SAMPLE_RATE") != "",
+		"OPENAI_TTS_API_KEY":        os.Getenv("OPENAI_TTS_API_KEY") != "",
+		"ALLOWED_ORIGINS":           os.Getenv("ALLOWED_ORIGINS") != "",
+		"PORT":                      os.Getenv("PORT") != "",
 	}
 
 	return map[string]interface{}{