CI: Test MDAnalysis Version Compatibility Matrix

[harryswift01]

To ensure robust compatibility and prevent regressions, we should expand the CI setup to test against multiple versions of MDAnalysis. This will help us validate that our codebase works reliably across a range of supported versions and catch breaking changes early.

• Test multiple versions of MDAnalysis
• Use a matrix strategy in CI to cover combinations
• Pin specific versions of MDAnalysis where needed
• Optionally use Conda environments for dependency resolution
• Define version ranges in pyproject.toml for reproducibility