Add PHPUnit configuration and expand notification failure tests

[JLG-WOCFR-DEV]

Summary

• add a phpunit.xml.dist configuration and composer scripts to run the PHP test suite with JUnit output
• cover the wp_mail failure path in NotificationManagerTest and ignore PHPUnit artifacts in git
• run composer test:php in CI before the existing Node jobs and document how to execute the PHP suite locally

Testing

• composer test:php (fails: existing suite raises Patchwork exceptions in LinkScanStatusTest when redefining WordPress functions)

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https://chatgpt.com/codex/tasks/task_e_68f39f776348832e9fa83eb1cbdee1ca

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Gate PHP tests before fixing current failures

The workflow now installs Composer dependencies and runs composer test:php ahead of the existing JS jobs, but the commit summary explicitly notes that this command currently fails with Patchwork exceptions in LinkScanStatusTest. Shipping this as-is will make the entire workflow red on every push or PR, so none of the JavaScript or Playwright checks will run and merges will be blocked. Consider either fixing the failing PHPUnit suite or temporarily marking the step as allowed-to-fail until the PHP tests are stable.

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