Add check for Email safety (Reroute email)

Problem/Motivation

In this Drupal application, lower environments (such as development, testing, or staging) may still be able to send real emails to end users, which can leak test data, confuse users, or unintentionally trigger real-world workflows during testing.

Steps to reproduce

Proposed resolution

Add a new Security FitCheck plugin LowEnvironmentEmailRerouteCheck that:

• Detects when the site is running in a non-production environment (for example via environment settings or configuration flags).
• Checks the mail system configuration to ensure outgoing emails are rerouted to a safe sink address (or disabled) instead of being sent to real recipients.
• Fails with FitWeight::High when a lower environment can send mail to arbitrary addresses, listing the current mail settings and recommending enabling an email reroute/sandbox configuration.

Remaining tasks

User interface changes

API changes

Data model changes