FEATURE: Add E2E test setup

[JamesAlias]

Add E2E test suite and named second factors

• Feature: E2E test infrastructure: Adds a Playwright/Cucumber BDD test suite covering the four supported 2FA enforcement configurations (default, enforce-for-all, enforce-for-provider, enforce-for-role).
  Includes Dockerized system-under-test environments for Neos 8 and Neos 9, and a GitHub Actions workflow that runs the full suite on CI.
• Feature: Named second factors: Adds an optional name field to the SecondFactor model so users can label their TOTP authenticator when registering it (e.g. "Work phone", "YubiKey app").
  -Bugfix: Neos 9 compatibility fix: Changes $this->persistenceManager->persistAll() to a null-safe call (?->) because in Neos 9 ActionControllers do not have the persistenceManager injected.
• Chore: Configuration housekeeping: Moves the plugin's own settings block out of Settings.yaml into a dedicated Settings.2FA.yaml.
• DX: Developer tooling: Adds a Makefile with targets for building, starting, and running the test environments and also updated Readme.