refactor(model): support string type in JSON scan methods

Enhance Scan methods in StringArray, ExtraData, MessageSegments, and
SystemNotificationExtra to accept both []byte and string types from database.
Uses type switch for more flexible type handling.

internal/model/message.go

@@ -101,11 +101,16 @@ func (e *ExtraData) Scan(value any) error {
 	if value == nil {
 		return nil
 	}
-	bytes, ok := value.([]byte)
-	if !ok {
-		return errors.New("type assertion to []byte failed")
+	var data []byte
+	switch v := value.(type) {
+	case []byte:
+		data = v
+	case string:
+		data = []byte(v)
+	default:
+		return errors.New("type assertion to []byte or string failed")
 	}
-	return json.Unmarshal(bytes, e)
+	return json.Unmarshal(data, e)
 }
 
 // MessageSegmentData 单个消息段的数据
@@ -131,11 +136,16 @@ func (s *MessageSegments) Scan(value any) error {
 		*s = nil
 		return nil
 	}
-	bytes, ok := value.([]byte)
-	if !ok {
-		return errors.New("type assertion to []byte failed")
+	var data []byte
+	switch v := value.(type) {
+	case []byte:
+		data = v
+	case string:
+		data = []byte(v)
+	default:
+		return errors.New("type assertion to []byte or string failed")
 	}
-	return json.Unmarshal(bytes, s)
+	return json.Unmarshal(data, s)
 }
 
 // Message 消息实体