[Feature Request] Have the black and grey squares in Song-Editor change based on the signature

### Enhancement Summary

Basically, the black and grey squares are always showing in 4/4 time, independent of the time signature used. Changing it would allow for easier tracking of the time signature.

### Implementation Details / Mockup

The implementation should be similar to how the 4/4 time coloring schema is done. If N/D is the time signature, the color should change after N*D beats, and one bar should be N beats long.

This poses a question of how automating the signature would effect the Song-Editor UI. Regarding that, I'm open to suggestions.

### Please search the issue tracker for existing feature requests before submitting your own.

- [X] I have searched all existing issues and confirmed that this is not a duplicate.

Start by locating the Song-Editor implementation and the existing 4/4 time-coloring logic. Determine how the N/D signature should control bar length and color changes, resolve the UI behavior question, and verify that the editor visibly tracks the selected time signature.

Written by the indexing model from the issue text.