Fix temperature not being set to 0 due to json omitempty

The issue was caused by the `omitempty` tag in the Go struct, which prevented the `temperature` field from being included in the JSON output when it was set to 0.

Signed-off-by: Butui Hu <hot123tea123@gmail.com>

relay/channel/cloudflare/dto.go

@@ -9,7 +9,7 @@ type CfRequest struct {
 	Prompt      string        `json:"prompt,omitempty"`
 	Raw         bool          `json:"raw,omitempty"`
 	Stream      bool          `json:"stream,omitempty"`
-	Temperature float64       `json:"temperature,omitempty"`
+	Temperature *float64      `json:"temperature,omitempty"`
 }
 
 type CfAudioResponse struct {