feat(oauth): migrate GitHub user identification from login to numeric ID

model/user.go

@@ -540,6 +540,14 @@ func (user *User) FillUserByGitHubId() error {
 	return nil
 }
 
+// UpdateGitHubId updates the user's GitHub ID (used for migration from login to numeric ID)
+func (user *User) UpdateGitHubId(newGitHubId string) error {
+	if user.Id == 0 {
+		return errors.New("user id is empty")
+	}
+	return DB.Model(user).Update("github_id", newGitHubId).Error
+}
+
 func (user *User) FillUserByDiscordId() error {
 	if user.DiscordId == "" {
 		return errors.New("discord id 为空！")