[3.0]: Migrate to jQuery 4.0.0

[dragomano]

https://blog.jquery.com/2026/01/17/jquery-4-0-0/

[Oldiesmann]

A quick test on a test board seems to indicate there won't be any problems if we decide to go this way, but more thorough testing is needed to ensure it won't break anything.

[jdarwood007]

We will look at this after the theme changes have occurred