Hyprland's exec_cmd does not source the shell PATH, so plain
wallpaper-fetcher failed from the keybinding; use ~/.local/bin. Binary
rebuilt (5.3MB -> 2.6MB) and the keybinding now fetches technics.
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.