Move all omarchy runtime state (themes, backgrounds, current theme)
from ~/.config/omarchy/current to ~/.local/state/omarchy/current
to keep the config dir free of generated files. Add mise task for
recreating symlinks and update credential helpers for tea.
Add a compiled wallpaper-fetcher binary that downloads images from backiee.com, and a set-wallpaper.sh wrapper that downloads a random wallpaper and sets it as the desktop background via awww.