fix: 修复未绑定外部邮箱的新用户登录被二次验证阻断的问题

backend/controllers/login_verification.go

@@ -12,6 +12,7 @@ import (
 	"git.pcux.cn/xuans/Smail/dto/response"
 	"git.pcux.cn/xuans/Smail/models"
 	"git.pcux.cn/xuans/Smail/services/access"
+	"git.pcux.cn/xuans/Smail/services/externalemail"
 	"git.pcux.cn/xuans/Smail/services/verification"
 	"git.pcux.cn/xuans/Smail/session"
 	"git.pcux.cn/xuans/Smail/utils/array"
@@ -91,6 +92,9 @@ func beginLoginVerification(user *models.User, remoteIP string) (map[string]any,
 	}
 	binding, err := runtime.external.FindVerifiedPrimaryByUser(user.ID)
 	if err != nil {
+		if errors.Is(err, externalemail.ErrBindingNotFound) {
+			return nil, nil
+		}
 		return nil, errLoginVerificationUnavailable
 	}
 	email, err := runtime.external.Decrypt(*binding)

backend/controllers/login_verification_policy_test.go

@@ -1,6 +1,10 @@
 package controllers
 
-import "testing"
+import (
+	"testing"
+
+	"git.pcux.cn/xuans/Smail/models"
+)
 
 func TestLoginVerificationPolicyEnabled(t *testing.T) {
 	tests := []struct {
@@ -24,3 +28,17 @@ func TestLoginVerificationPolicyEnabled(t *testing.T) {
 		})
 	}
 }
+
+func TestBeginLoginVerification_NoExternalEmail(t *testing.T) {
+	user := &models.User{
+		ID: 99999,
+		Account: "test_no_email",
+	}
+	res, err := beginLoginVerification(user, "127.0.0.1")
+	if err != nil {
+		t.Fatalf("expected nil error for user without external email, got: %v", err)
+	}
+	if res != nil {
+		t.Fatalf("expected nil challenge result for user without external email, got: %v", res)
+	}
+}