Probability maps from new reconstructions, data-derived background distributions and time windows

[G-Sommani]

This is the updated version of Alertstack that I used in the new analysis already in the nu-sources WG folder: https://github.com/icecube/wg-nu-sources/tree/main/2026_Alertstack_IceCat2

Many things have changed, in particular:

• The format of the probability maps is now different (they are multi-order maps, with pixels of different dimensions);
• A system to handle non-isotropic source catalogs was also implemented;
• Time windows are now available.

Further updates concern making the code significantly faster to facilitate future analyses, using the correct interpretation of the signalness, and new libraries dedicated to handling the results.