Tools needed: Logo partition for u-boot

[m-weigand]

We need proper tooling, documentation, and packaging for handling of the logo partition.

The logo partition holds complete screen images that u-boot (the boot loader) uses to display things on the epd (eink) screen. This includes:

• an "PN is off" logo
• charging anomations
• boot entry screens (i.e., boot from os1)

Right now, changing these logos is very involved, see the current pre-tooling here:

https://github.com/PNDeb/pinenote-debian-image/tree/trixie/custom_logos_uboot

It would be nice to have better documentation and proper tools to change logos. Common use cases would be:

• When we change the boot order, then this should be reflected in the shown screen content