Add packaging/arch PKGBUILD and Forgejo Actions workflows

- packaging/arch/PKGBUILD: builds and publishes breadpad to [breadway] repo
- .forgejo/workflows/mirror.yml: mirrors every push/tag to GitHub
- .forgejo/workflows/package.yml: builds on tag, publishes to Forgejo registry

Requires FORGEJO_TOKEN and GITHUB_MIRROR_TOKEN secrets in Forgejo.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.forgejo/workflows/mirror.yml

@@ -0,0 +1,20 @@
+name: Mirror to GitHub
+
+on:
+  push:
+    branches: ['**']
+    tags: ['**']
+
+jobs:
+  mirror:
+    runs-on: [self-hosted, hestia]
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Push to GitHub
+        run: |
+          git remote add github \
+            "https://x-access-token:${{ secrets.GITHUB_MIRROR_TOKEN }}@github.com/Breadway/breadpad.git"
+          git push github --mirror

.forgejo/workflows/package.yml

@@ -0,0 +1,46 @@
+name: Build and publish package
+
+on:
+  push:
+    tags: ['v*']
+
+jobs:
+  package:
+    runs-on: [self-hosted, hestia]
+    container:
+      image: archlinux:latest
+      options: --privileged
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set version
+        run: echo "VERSION=${GITHUB_REF_NAME#v}" >> $GITHUB_ENV
+
+      - name: Install build dependencies
+        run: pacman -Syu --noconfirm base-devel git rust cargo gtk4 gtk4-layer-shell
+
+      - name: Create builder user
+        run: useradd -m builder
+
+      - name: Prepare source
+        run: |
+          git archive --format=tar.gz \
+            --prefix=breadpad-${VERSION}/ \
+            HEAD > packaging/arch/breadpad-${VERSION}.tar.gz
+          SHA=$(sha256sum packaging/arch/breadpad-${VERSION}.tar.gz | awk '{print $1}')
+          sed -i "s/^pkgver=.*/pkgver=${VERSION}/" packaging/arch/PKGBUILD
+          sed -i "s/^sha256sums=.*/sha256sums=('${SHA}')/" packaging/arch/PKGBUILD
+          cp -r . /home/builder/src
+          chown -R builder:builder /home/builder/src
+
+      - name: Build package
+        run: su builder -c "cd /home/builder/src/packaging/arch && makepkg -sf --noconfirm"
+
+      - name: Publish to Forgejo registry
+        run: |
+          PKG=$(find /home/builder/src/packaging/arch -name '*.pkg.tar.zst' | head -1)
+          curl -fsS -X PUT \
+            -H "Authorization: token ${{ secrets.FORGEJO_TOKEN }}" \
+            --upload-file "${PKG}" \
+            "https://git.breadway.dev/api/packages/breadway/arch/push?distrib=breadway"