30: mlx 08 optional interaction 42 pattern colours

[semere-meb]

Summary

Pattern now drawn distinctively.

Fixes #30

Changes

• Renamed src/ui.py to src/maze_view.py
• New MazeView.render_pattern to render the pattern cells
• Now using mazegen from PyPI

Testing

• make lint passes locally
• make test passes locally
• Manually tested the behavior described above

Checklist

• PR title follows <TICKET-ID>: short description
• Linked to the correct issue (Fixes #... above)
• No unrelated changes bundled into this diff
• Updated README if this changes user-facing behavior (config keys, controls, etc.)