fix(customer): cast website and store ids to int in EmailNotification (#40469)

[lbajsarowicz]

Description (*)

Cast website and store IDs to int in EmailNotification::getWebsiteStoreId() so the return value matches the declared int return type when StoreManager/Website return IDs as strings.

Fixed Issues (if relevant)

Fixes #40469

Manual testing scenarios (*)

1. Create a custom module that sends welcome email via Magento\Customer\Model\EmailNotification::newAccount($customer).
2. Trigger welcome email (e.g. after customer registration or programmatically).
3. Verify no type error: "Return value must be of type int, string returned" and that the email is sent.

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined sections require an update
• All automated tests passed successfully (all builds are green)

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[lbajsarowicz]

@magento run all tests

[magento-automated-testing]

Pull Requests are not mergeable to the mainline. Please merge the latest mainlines to your Pull Requests and restart the builds.

[lbajsarowicz]

@magento run all tests