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.

.forgejo/workflows/release.yml

@@ -0,0 +1,59 @@
+name: release
+
+on:
+  push:
+    tags: ["v*"]
+
+jobs:
+  build:
+    runs-on: [self-hosted, hestia]
+    steps:
+      - name: checkout
+        run: |
+          set -euo pipefail
+          rm -rf src && mkdir src
+          git clone --branch "${GITHUB_REF_NAME}" --depth 1 \
+            "https://git.breadway.dev/${GITHUB_REPOSITORY}.git" src
+
+      - name: build
+        run: cd src && cargo build --release --locked
+
+      - name: test
+        run: cd src && cargo test --release --locked
+
+      - name: prepare artifacts
+        run: |
+          set -euo pipefail
+          VERSION="${GITHUB_REF_NAME#v}"
+          PKG_DIR="/srv/breadway-dl/breadcrumbs/${VERSION}"
+          mkdir -p "${PKG_DIR}"
+          cp src/target/release/breadcrumbs "${PKG_DIR}/breadcrumbs-x86_64"
+          strip "${PKG_DIR}/breadcrumbs-x86_64"
+          sha256sum "${PKG_DIR}/breadcrumbs-x86_64" | awk '{print $1}' \
+            > "${PKG_DIR}/breadcrumbs-x86_64.sha256"
+          cp src/breadcrumbs.example.toml "${PKG_DIR}/"
+          cp src/LICENSE "${PKG_DIR}/"
+          cp src/bakery.toml "${PKG_DIR}/bakery.toml"
+          cp src/contrib/breadcrumbs.service "${PKG_DIR}/"
+          ln -sfn "${VERSION}" "/srv/breadway-dl/breadcrumbs/latest"
+
+      - name: regenerate index.json
+        run: |
+          set -euo pipefail
+          rm -rf /tmp/bread-ecosystem-ci
+          git clone https://git.breadway.dev/Breadway/bread-ecosystem.git /tmp/bread-ecosystem-ci
+          bash /tmp/bread-ecosystem-ci/scripts/gen-index.sh
+
+      - name: upload to GitHub Release
+        env:
+          GH_TOKEN: ${{ secrets.GH_RELEASE_TOKEN }}
+        run: |
+          set -euo pipefail
+          VERSION="${GITHUB_REF_NAME#v}"
+          PKG_DIR="/srv/breadway-dl/breadcrumbs/${VERSION}"
+          gh release create "${GITHUB_REF_NAME}" --repo Breadway/breadcrumbs \
+            --title "breadcrumbs v${VERSION}" --generate-notes 2>/dev/null || true
+          gh release upload "${GITHUB_REF_NAME}" --repo Breadway/breadcrumbs \
+            "${PKG_DIR}/breadcrumbs-x86_64" \
+            "${PKG_DIR}/breadcrumbs-x86_64.sha256" \
+            --clobber