feat(relay): add debug logging for Gemini request body and introduce flexible speech configuration

relay/channel/gemini/dto.go

@@ -140,6 +140,7 @@ type GeminiChatGenerationConfig struct {
 	Seed               int64                 `json:"seed,omitempty"`
 	ResponseModalities []string              `json:"responseModalities,omitempty"`
 	ThinkingConfig     *GeminiThinkingConfig `json:"thinkingConfig,omitempty"`
+	SpeechConfig       json.RawMessage       `json:"speechConfig,omitempty"` // RawMessage to allow flexible speech config
 }
 
 type GeminiChatCandidate struct {

relay/relay-gemini.go

@@ -155,6 +155,10 @@ func GeminiHelper(c *gin.Context) (openaiErr *dto.OpenAIErrorWithStatusCode) {
 		return service.OpenAIErrorWrapperLocal(err, "marshal_text_request_failed", http.StatusInternalServerError)
 	}
 
+	if common.DebugEnabled {
+		println("Gemini request body: %s", string(requestBody))
+	}
+
 	resp, err := adaptor.DoRequest(c, relayInfo, bytes.NewReader(requestBody))
 	if err != nil {
 		common.LogError(c, "Do gemini request failed: "+err.Error())