fix: handle merge flow from email register endpoint

- Update registerEmail return type to include merge_required/merge_token
- Redirect to /merge/{token} when email register returns merge_required

src/api/auth.ts

@@ -78,7 +78,12 @@ export const authApi = {
   registerEmail: async (
     email: string,
     password: string,
-  ): Promise<{ message: string; email: string }> => {
+  ): Promise<{
+    message: string;
+    email?: string;
+    merge_required?: boolean;
+    merge_token?: string;
+  }> => {
     const response = await apiClient.post('/cabinet/auth/email/register', {
       email,
       password,

src/pages/Profile.tsx

@@ -148,7 +148,12 @@ export default function Profile() {
   const registerEmailMutation = useMutation({
     mutationFn: ({ email, password }: { email: string; password: string }) =>
       authApi.registerEmail(email, password),
-    onSuccess: async () => {
+    onSuccess: async (response) => {
+      // Backend returns merge_required when email belongs to another user
+      if (response.merge_required && response.merge_token) {
+        navigate(`/merge/${response.merge_token}`, { replace: true });
+        return;
+      }
       setSuccess(t('profile.emailSent'));
       setError(null);
       setEmail('');