fix: add specific error message for duplicate SRP imports (#37743)

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## **Description**

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CHANGELOG entry: fix error message when trying to import an SRP with an
account that is already imported via private key

## **Related issues**

Fixes: https://consensyssoftware.atlassian.net/browse/MUL-491

## **Manual testing steps**

1. Import private key account
2. Import SRP that includes this private key account
3. Verify that the error message "The account you are trying to import
is a duplicate." is shown

## **Screenshots/Recordings**

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### **Before**

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### **After**

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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Show a specific error when an imported SRP contains a duplicate
account, with new i18n strings and tests validating behavior.
> 
> - **Import SRP UI (`ui/pages/multi-srp/import-srp/import-srp.tsx`)**:
> - Handle duplicate-account import errors explicitly by mapping
controller error to `t('srpImportDuplicateAccountError')`; fall back to
`srpAlreadyImportedError`.
> - **i18n (`app/_locales/en/messages.json`,
`app/_locales/en_GB/messages.json`)**:
> - Add `srpImportDuplicateAccountError` message: "The account you are
trying to import is a duplicate."
> - **Tests (`ui/pages/multi-srp/import-srp/import-srp.test.tsx`)**:
> - Add error-handling tests covering duplicate-account vs generic
import errors; ensure button disables, no navigation, and no toast on
error.
>   - Minor import updates to support test setup.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
7adca32. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: mathieuartu

app/_locales/en/messages.json

@@ -1,13 +1,15 @@
 import React from 'react';
 import { fireEvent, waitFor } from '@testing-library/react';
+import { userEvent } from '@testing-library/user-event';
 import configureMockStore from 'redux-mock-store';
 import thunk from 'redux-thunk';
-import { userEvent } from '@testing-library/user-event';
-import { renderWithProvider } from '../../../../test/lib/render-helpers-navigate';
+// eslint-disable-next-line import/no-restricted-paths
+import messages from '../../../../app/_locales/en/messages.json';
 import mockState from '../../../../test/data/mock-state.json';
-import { importMnemonicToVault } from '../../../store/actions';
-import { DEFAULT_ROUTE } from '../../../helpers/constants/routes';
+import { renderWithProvider } from '../../../../test/lib/render-helpers-navigate';
 import { setShowNewSrpAddedToast } from '../../../components/app/toast-master/utils';
+import { DEFAULT_ROUTE } from '../../../helpers/constants/routes';
+import { importMnemonicToVault } from '../../../store/actions';
 import { ImportSrp } from './import-srp';
 
 jest.mock('../../../store/actions', () => ({
@@ -95,4 +97,65 @@ describe('ImportSrp', () => {
       expect(setShowNewSrpAddedToast).toHaveBeenCalledWith(true);
     });
   });
+
+  describe('error handling', () => {
+    const testImportError = async (
+      errorMessage: string,
+      expectedErrorMessage: string,
+    ) => {
+      const mockStore = configureMockStore([thunk])(mockState);
+
+      // Mock importMnemonicToVault to reject with the specified error
+      (importMnemonicToVault as jest.Mock).mockReturnValueOnce(
+        jest.fn().mockRejectedValue(new Error(errorMessage)),
+      );
+
+      const { queryByTestId, getByText } = renderWithProvider(
+        <ImportSrp />,
+        mockStore,
+      );
+
+      const srpNote = queryByTestId('srp-input-import__srp-note');
+      expect(srpNote).toBeInTheDocument();
+
+      srpNote?.focus();
+
+      if (srpNote) {
+        await userEvent.type(srpNote, TEST_SEED);
+      }
+
+      const confirmSrpButton = queryByTestId('import-srp-confirm');
+      expect(confirmSrpButton).not.toBeDisabled();
+
+      if (confirmSrpButton) {
+        fireEvent.click(confirmSrpButton);
+      }
+
+      // Wait for error to be displayed
+      await waitFor(() => {
+        expect(getByText(expectedErrorMessage)).toBeInTheDocument();
+      });
+
+      // Verify the button is now disabled due to error
+      expect(confirmSrpButton).toBeDisabled();
+
+      // Verify navigation did not happen
+      expect(mockNavigate).not.toHaveBeenCalledWith(DEFAULT_ROUTE);
+      expect(setShowNewSrpAddedToast).not.toHaveBeenCalled();
+    };
+
+    it('should display duplicate account error when trying to import a duplicate account', async () => {
+      await testImportError(
+        'KeyringController - The account you are trying to import is a duplicate',
+        messages.srpImportDuplicateAccountError.message,
+      );
+    });
+
+    it('should display already imported error for any other import error', async () => {
+      await testImportError(
+        'Some other error',
+        messages.srpAlreadyImportedError.message,
+      );
+    });
+  });
 });

app/_locales/en_GB/messages.json

@@ -81,7 +81,14 @@ export const ImportSrp = () => {
       navigate(DEFAULT_ROUTE);
       dispatch(setShowNewSrpAddedToast(true));
     } catch (error) {
-      setSrpError(t('srpAlreadyImportedError'));
+      switch ((error as Error)?.message) {
+        case 'KeyringController - The account you are trying to import is a duplicate':
+          setSrpError(t('srpImportDuplicateAccountError'));
+          break;
+        default:
+          setSrpError(t('srpAlreadyImportedError'));
+          break;
+      }
     }
   }