feat: Handle errors, validate model names, and calculate quota usage

- Improved error handling in various modules for better stability and responsiveness.
- Optimized code in several files for improved efficiency and readability.
- Enhanced user experience by providing more detailed error responses in the controller.
- Strengthened security by ignoring sensitive files in `.gitignore`.

relay/channel/openai/token.go

@@ -27,7 +27,7 @@ func InitTokenEncoders() {
 	if err != nil {
 		logger.FatalLog(fmt.Sprintf("failed to get gpt-4 token encoder: %s", err.Error()))
 	}
-	for model, _ := range common.ModelRatio {
+	for model := range common.ModelRatio {
 		if strings.HasPrefix(model, "gpt-3.5") {
 			tokenEncoderMap[model] = gpt35TokenEncoder
 		} else if strings.HasPrefix(model, "gpt-4") {