Drop pacman packaging, bakery-only distribution

bakery already fully covers what the PKGBUILD provided (binary, systemd
--user service where applicable, 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.

packaging/arch/PKGBUILD

@@ -1,39 +0,0 @@
-# Maintainer: Breadway <rileyhorsham@gmail.com>
-
-pkgname=breadbox
-pkgver=0.1.0
-pkgrel=1
-pkgdesc="App launcher for Hyprland / Wayland"
-arch=('x86_64')
-url="https://github.com/Breadway/breadbox"
-license=('MIT')
-# Some Rust deps (ring/mlua) build vendored C/asm into static archives; makepkg's
-# default -flto=auto emits GCC LTO bitcode the Rust (lld) link cannot read,
-# causing undefined-symbol errors. Disable LTO.
-options=(!lto !debug)
-depends=('gtk4' 'gtk4-layer-shell' 'librsvg')
-optdepends=(
-  'hyprland: window and workspace integration'
-)
-makedepends=('rust' 'cargo')
-source=("${pkgname}-${pkgver}.tar.gz")
-sha256sums=('SKIP')
-
-build() {
-  cd "${srcdir}/${pkgname}-${pkgver}"
-  cargo build --release --locked
-}
-
-check() {
-  cd "${srcdir}/${pkgname}-${pkgver}"
-  cargo test --release --locked --workspace
-}
-
-package() {
-  cd "${srcdir}/${pkgname}-${pkgver}"
-  install -Dm755 target/release/breadbox      "${pkgdir}/usr/bin/breadbox"
-  install -Dm755 target/release/breadbox-sync "${pkgdir}/usr/bin/breadbox-sync"
-  install -Dm644 packaging/breadbox-sync.service \
-    "${pkgdir}/usr/lib/systemd/user/breadbox-sync.service"
-  install -Dm644 LICENSE "${pkgdir}/usr/share/licenses/${pkgname}/LICENSE"
-}