feat: Add user notification settings with quota warning and multiple notification methods

- Implement user notification settings with email and webhook options
- Add new user settings for quota warning threshold and notification preferences
- Create backend API and database support for user notification configuration
- Enhance frontend personal settings with notification configuration UI
- Support custom notification email and webhook URL
- Add service layer for sending user notifications

dto/openai_request.go

@@ -18,6 +18,7 @@ type GeneralOpenAIRequest struct {
 	Model               string          `json:"model,omitempty"`
 	Messages            []Message       `json:"messages,omitempty"`
 	Prompt              any             `json:"prompt,omitempty"`
+	Prefix              any             `json:"prefix,omitempty"`
 	Suffix              any             `json:"suffix,omitempty"`
 	Stream              bool            `json:"stream,omitempty"`
 	StreamOptions       *StreamOptions  `json:"stream_options,omitempty"`