[Bug]: Cross-Instance Authentication Corruption via Hardcoded `ec_token` Key

The EmbeddedChat authentication logic hardcodes the localStorage key to ec_token in packages/react/src/lib/auth.js. This prevents multiple instances of EmbeddedChat from co-existing on the same domain with independent sessions.

If two EmbeddedChat instances (for example, a Sales Bot and a Support Bot) are embedded on the same page or domain, logging into one instance overwrites the authentication token of the other.

Reproduction Steps

1. Embed two instances of EmbeddedChat on the same page.
2. Log in to Instance A.
3. Log in to Instance B.
4. Refresh the page.

Result: Instance A is logged in as Instance B’s user (or ends up with an invalid token), because the shared ec_token value was overwritten.

Jest Test

const localStorageMock = (function () {
  let store = {};
  return {
    getItem: (key) => store[key] || null,
    setItem: (key, value) => {
      store[key] = value.toString();
    },
    removeItem: (key) => {
      delete store[key];
    },
    clear: () => {
      store = {};
    },
  };
})();

Object.defineProperty(global, 'localStorage', {
  value: localStorageMock,
});

import { getTokenStorage } from './auth';

describe('Cross-Instance Authentication Corruption', () => {
  beforeEach(() => {
    localStorage.clear();
    jest.clearAllMocks();
  });

  const getLocalStorageKey = () => 'ec_token';

  test('Two seemingly independent instances overwrite each other\'s tokens', async () => {
    const auth = getTokenStorage(false);
    const { saveToken, getToken } = auth;

    // Simulate Instance A login
    const instanceAToken = 'token_for_instance_A';
    await saveToken(instanceAToken);

    expect(localStorage.getItem(getLocalStorageKey())).toBe(instanceAToken);
    expect(await getToken()).toBe(instanceAToken);

    // Simulate Instance B login
    const instanceBToken = 'token_for_instance_B';
    await saveToken(instanceBToken);

    // Instance A token is overwritten
    expect(localStorage.getItem(getLocalStorageKey())).toBe(instanceBToken);

    const currentToken = await getToken();
    expect(currentToken).not.toBe(instanceAToken);
    expect(currentToken).toBe(instanceBToken);
  });
});

Expected Behavior

The token storage key should be configurable or automatically namespaced to allow multiple isolated EmbeddedChat instances on the same domain.

Start in packages/react/src/lib/auth.js, especially getTokenStorage(false), and reproduce the two-instance scenario with the Jest test described in the issue. Trace how saveToken and getToken derive their localStorage key. Done means separate EmbeddedChat instances retain independent tokens, with coverage for saving and retrieving both tokens.