fix(api/auth): reset count variable before uniqueness checks

Fix a bug where the count variable was not reset before checking
email and phone uniqueness. This could cause false positives if
a previous check had count > 0, incorrectly reporting that email
or phone already exists when they don't.

- Reset count to 0 before email check
- Reset count to 0 before phone check

api/auth/register.go

@@ -55,6 +55,7 @@ func register(x *vigo.X, req *RegisterRequest) (*AuthResponse, error) {
 
 	// 检查邮箱是否已存在
 	if req.Email != "" {
+		count = 0 // 重置计数器
 		if err := cfg.DB().Model(&models.User{}).Where("email = ?", req.Email).Count(&count).Error; err != nil {
 			return nil, vigo.ErrInternalServer.WithError(err)
 		}
@@ -65,6 +66,7 @@ func register(x *vigo.X, req *RegisterRequest) (*AuthResponse, error) {
 
 	// 检查手机是否已存在
 	if req.Phone != "" {
+		count = 0 // 重置计数器
 		if err := cfg.DB().Model(&models.User{}).Where("phone = ?", req.Phone).Count(&count).Error; err != nil {
 			return nil, vigo.ErrInternalServer.WithError(err)
 		}