fix: openai response should contains model

- Update model attributes in `claudeHandler` for `relay-claude.go`
- Implement model type for fullTextResponse in `relay-gemini.go`
- Add new `Model` field to `OpenAITextResponse` struct in `relay.go`

controller/relay-claude.go

@@ -211,6 +211,7 @@ func claudeHandler(c *gin.Context, resp *http.Response, promptTokens int, model
 		}, nil
 	}
 	fullTextResponse := responseClaude2OpenAI(&claudeResponse)
+	fullTextResponse.Model = model
 	completionTokens := countTokenText(claudeResponse.Completion, model)
 	usage := Usage{
 		PromptTokens:     promptTokens,