fix for phone generation on email signup

internal/store/memory/phone_change.go

@@ -42,7 +42,11 @@ func (s *PhoneChangeStore) ChangePhone(ctx context.Context, req domain.PhoneChan
 		}
 	}
 	currentPhone := u.Phone
+	currentSignupEmail := u.SignupEmail
 	u.Phone = req.Phone
+	if req.SignupEmail != "" {
+		u.SignupEmail = req.SignupEmail
+	}
 	s.users.byID[req.UserID] = u
 
 	date := req.Date
@@ -62,6 +66,7 @@ func (s *PhoneChangeStore) ChangePhone(ctx context.Context, req domain.PhoneChan
 		if err != nil {
 			// 保持内存替身与 PG 的 user+event 原子可见语义。
 			u.Phone = currentPhone
+			u.SignupEmail = currentSignupEmail
 			s.users.byID[req.UserID] = u
 			s.users.mu.Unlock()
 			return domain.PhoneChangeResult{}, err

internal/store/memory/users.go

@@ -2,6 +2,7 @@ package memory
 
 import (
 	"context"
+	"fmt"
 	"sort"
 	"strings"
 	"sync"
@@ -72,6 +73,23 @@ func (s *UserStore) ByPhone(_ context.Context, phone string) (domain.User, bool,
 	return domain.User{}, false, nil
 }
 
+// ByEmail looks up an email-signup account by its signup_email (see
+// domain.NewEmailSignupDisplayPhone). Mirrors postgres.UserStore.ByEmail.
+func (s *UserStore) ByEmail(_ context.Context, email string) (domain.User, bool, error) {
+	email = strings.ToLower(strings.TrimSpace(email))
+	if email == "" {
+		return domain.User{}, false, nil
+	}
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	for _, u := range s.byID {
+		if u.SignupEmail != "" && strings.ToLower(u.SignupEmail) == email {
+			return u, true, nil
+		}
+	}
+	return domain.User{}, false, nil
+}
+
 func (s *UserStore) ByPhones(_ context.Context, phones []string) ([]domain.User, error) {
 	if len(phones) == 0 {
 		return nil, nil
@@ -377,6 +395,14 @@ func (s *UserStore) Create(_ context.Context, u domain.User) (domain.User, error
 			}
 		}
 	}
+	signupEmail := strings.ToLower(strings.TrimSpace(u.SignupEmail))
+	if signupEmail != "" {
+		for _, existing := range s.byID {
+			if existing.SignupEmail != "" && strings.ToLower(existing.SignupEmail) == signupEmail {
+				return domain.User{}, fmt.Errorf("create user: signup email occupied")
+			}
+		}
+	}
 	u.ID = s.nextID
 	s.nextID++
 	s.byID[u.ID] = u