Fix CWE-20 vulnerability in environment variable validation

[kolega-dev-github-app]

Summary

This PR fixes a high-severity CWE-20 (Insufficient Input Validation) vulnerability in the environment variable validation logic. It replaces the incomplete blocklist approach with a comprehensive whitelist-based validation system to address the root cause and follow security best practices.

Changes

• Implemented a whitelist-based validation system with multiple security layers:
  • Name whitelist to only allow pre-approved variable names
  • Value validation with custom validators for different variable categories
  • Base validation to check for common injection vectors
• Added comprehensive value validators for different variable types (e.g., paths, identifiers)
• Maintained existing code style and did not introduce new vulnerabilities

Testing

The changes have been thoroughly tested to ensure the fix addresses the vulnerability without breaking existing functionality.