fix(security): replace eval with safe AST evaluator

[sanzverseoff]

Pull Request Template

Description

• What changes are being made?

• Why are these changes necessary?

• Which issues or tickets does this PR close or relate to?

  • Related issue: #

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Other (please specify):

Checklist

• Code has been linted.
• Documentation has been updated (if needed).
• Tests have been added or updated (if needed).
• Any breaking changes have been communicated to the team.

Screenshots or Recordings (if applicable)

Additional Information

[codecov]

Codecov Report

❌ Patch coverage is 96.15385% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/tirith/core/core.py	96.15%	1 Missing and 1 partial ⚠️

Files with missing lines	Coverage Δ
src/tirith/core/core.py	88.34% <96.15%> (+2.56%)	⬆️

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