feat: Add automorphism group for antimagma

[limakzi]

This partially solves #204.

[Copilot]

Pull Request Overview

Adds functionality to compute the automorphism group of a magma structure. This feature implements a method to find all automorphisms (structure-preserving bijective mappings) of a given magma.

• Implements MagmaAutomorphismGroup function that computes automorphisms by checking all permutations
• Adds comprehensive documentation with usage examples
• Includes test coverage verifying automorphism properties

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
lib/properties.gd	Declares the MagmaAutomorphismGroup attribute with documentation and examples
lib/properties.gi	Implements the automorphism group computation algorithm
tst/test_properties_magma_automorphism_group.tst	Adds tests verifying automorphism group properties

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}