完善站点运营设置：分路由管理、登录可见评论、邮件模板内联与关闭注册 SSR。

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/service/auth.go

@@ -86,6 +86,9 @@ var dummyPasswordHash, _ = bcrypt.GenerateFromPassword(
 
 // Register 用户注册
 func (s *AuthService) Register(username, email, password string) (*model.User, error) {
+	if err := NewOperations(s.db, nil).Filter("username", username, 0); err != nil {
+		return nil, err
+	}
 	// 检查用户名是否已存在
 	var count int64
 	s.db.Model(&model.User{}).Where("username = ?", username).Count(&count)
@@ -559,6 +562,9 @@ func (s *AuthService) ChangePassword(userID uint, oldPassword, newPassword strin
 // - email 可为空；非空时需符合邮箱格式且不与他人重复
 // - signature 不超过 255 字符
 func (s *AuthService) UpdateProfile(userID uint, nickname, email, signature string) (*model.User, error) {
+	if err := NewOperations(s.db, nil).Filter("username", nickname, userID); err != nil {
+		return nil, err
+	}
 	nickname = strings.TrimSpace(nickname)
 	if nickname == "" {
 		return nil, errors.New("昵称不能为空")