fix(account): clear the guest flag on a deeplink email link

ConfirmByToken attached the confirmed email to the account but, on the link path,
skipped ClearGuest — so a guest who bound an email via the one-tap deeplink stayed a
guest (the code-based flow clears it in the link service). Clear the flag on a free
link too, promoting the guest to a durable account; the profile live event then
refreshes the open session. Integration test added.

backend/internal/account/email.go

@@ -319,6 +319,11 @@ func (s *EmailService) ConfirmByToken(ctx context.Context, token string) (LinkCo
 		if err := s.store.confirmEmailIdentity(ctx, pend.id, pend.accountID, pend.email, s.now()); err != nil {
 			return LinkConfirmation{}, err
 		}
+		// Binding the first email promotes a guest to a durable account, matching the
+		// code-based link flow (which clears the guest flag in the link service).
+		if err := s.store.ClearGuest(ctx, pend.accountID); err != nil {
+			return LinkConfirmation{}, err
+		}
 		return LinkConfirmation{Purpose: purposeLink, Account: pend.accountID}, nil
 	default:
 		return LinkConfirmation{}, fmt.Errorf("account: unsupported confirmation purpose %q", pend.purpose)

backend/internal/inttest/email_test.go

@@ -394,3 +394,32 @@ func TestEmailAccountSeedsDisplayName(t *testing.T) {
 		t.Errorf("display name = %q, want the email local part %q", acc.DisplayName, local)
 	}
 }
+
+// TestConfirmByTokenLinkClearsGuest: binding an email to a guest via the deeplink
+// promotes the guest to a durable account (the deeplink path must match the
+// code-based link flow, which clears the guest flag).
+func TestConfirmByTokenLinkClearsGuest(t *testing.T) {
+	ctx := context.Background()
+	store := account.NewStore(testDB)
+	mailer := &capturingMailer{}
+	svc := account.NewEmailService(store, mailer, "https://erudit-game.ru")
+	guest, err := store.ProvisionGuest(ctx, "")
+	if err != nil {
+		t.Fatalf("provision guest: %v", err)
+	}
+	email := "guest-link-" + uuid.NewString() + "@example.com"
+
+	if err := svc.RequestLinkCode(ctx, guest.ID, email); err != nil {
+		t.Fatalf("request link: %v", err)
+	}
+	if _, err := svc.ConfirmByToken(ctx, tokenFromMail(t, mailer.lastBody)); err != nil {
+		t.Fatalf("confirm by token: %v", err)
+	}
+	acc, err := store.GetByID(ctx, guest.ID)
+	if err != nil {
+		t.Fatalf("get: %v", err)
+	}
+	if acc.IsGuest {
+		t.Error("linking an email via the deeplink must promote the guest to durable")
+	}
+}