[ecs] Integrate security rules into ECS (#32)

[coisa]

Summary

This pull request integrates recommended security rules into the Easy Coding Standard (ECS) configuration. It leverages PHPCS Security Audit sniffs and other best practices to ensure ECS identifies and alerts about insecure PHP code patterns, such as dangerous functions, missing escapes, lack of input validation, unsafe file handling, and insecure headers.

Changes

• Add and configure PHPCS Security Audit sniffs in ecs.php
• Prohibit dangerous functions (eval, backticks, system execution, etc.)
• Enforce input validation and output escaping
• Detect unsafe file and header usage
• Relates to Integrate security rules into ECS (Easy Coding Standard) #32

Testing

• Run Running code style checks and fixes...
• Review ECS output for detection of unsafe code patterns

Closes #32