Drop pacman packaging, bakery-only distribution

bakery already fully covers what the PKGBUILD provided (binary, dependency
declarations) except a LICENSE copy, which bakery.toml's new license_file
field now closes. Removes packaging/arch/ and .forgejo/workflows/package.yml;
adds the LICENSE artifact to each release/dev-release/beta-release
workflow's prepare step. Not pacman-installed inside BOS today (BOS already
consumes these apps exclusively via build-local.sh's skel-staging), so this
only removes the option to `pacman -S` outside of BOS/bakery.

bakery.toml

@@ -4,6 +4,7 @@ binaries = ["breadbar"]
 system_deps = ["gtk4", "gtk4-layer-shell", "wireplumber", "pipewire-pulse", "brightnessctl", "iw"]
 optional_system_deps = ["hyprland"]
 bread_deps = []
+license_file = "LICENSE"
 
 [config]
 dir = "~/.config/breadbar"