Mirror/symmetry and X-Ray for Fill Tool

One feature I’ve always missed in ArmorPaint is the ability to paint symmetrically using the Fill tool. Currently, I have to manually paint each triangle on both sides of the model or use a conventional brush, which doesn’t always provide the necessary precision. Additionally, X-Ray mode would also be valuable, as neither symmetry nor X-Ray are available for Fill.

Most other ArmorPaint tools already support symmetry and X-Ray, but I’m unsure how complex it would be to implement, considering Fill works differently—applying color via UV-based flood fill. However, I see this as a particularly useful feature.

I’m bringing up this discussion because I haven’t found any suggestions for this implementation and I think it's very useful.

So, formalizing my suggestion, it would be to add symmetry axes in the Fill tool's options menu, like the image bellow:

Start by tracing the Fill tool’s UV-based flood-fill behavior and compare how the other tools expose symmetry and X-Ray. Confirm how symmetry axes and X-Ray should appear in the Fill tool’s options menu, then verify that filling works correctly across the requested axes and through the model in X-Ray mode.

Written by the indexing model from the issue text.