feat: Add ARM64 Docker image support

- Added QEMU emulation to CI workflow for ARM64 builds
- Updated all build jobs to support linux/amd64,linux/arm64 platforms
- Use dynamic repository owner for image tags
- Sanitize branch names for Docker tags (replace / with -)
- Add fallback for git describe --tags

Cherry-picked from postalserver/postal PR postalserver#3516

Co-authored-by: aalonzolu <5524124+aalonzolu@users.noreply.github.com>
Co-authored-by: openhands <openhands@all-hands.dev>

Author: openhands-agent

.github/workflows/ci.yml

@@ -24,6 +24,7 @@ jobs:
       - uses: actions/checkout@v4
         with:
           fetch-depth: 0
+      - uses: docker/setup-qemu-action@v3
       - uses: docker/setup-buildx-action@v2
       - uses: docker/login-action@v2
         with:
@@ -33,11 +34,11 @@ jobs:
       - uses: docker/build-push-action@v4
         with:
           push: true
-          tags: ghcr.io/postalserver/postal:ci-${{ github.sha }}
+          tags: ghcr.io/${{ github.repository_owner }}/postal:ci-${{ github.sha }}
           cache-from: type=gha
           cache-to: type=gha,mode=max
           target: ci
-          platforms: linux/amd64
+          platforms: linux/amd64,linux/arm64
 
   test:
     name: Test Suite
@@ -54,10 +55,10 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
       - run: docker compose pull
         env:
-          POSTAL_IMAGE: ghcr.io/postalserver/postal:ci-${{ github.sha }}
+          POSTAL_IMAGE: ghcr.io/${{ github.repository_owner }}/postal:ci-${{ github.sha }}
       - run: docker compose run postal sh -c 'bundle exec rspec'
         env:
-          POSTAL_IMAGE: ghcr.io/postalserver/postal:ci-${{ github.sha }}
+          POSTAL_IMAGE: ghcr.io/${{ github.repository_owner }}/postal:ci-${{ github.sha }}
 
   release-branch:
     name: Release (branch)
@@ -80,20 +81,23 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
       - id: info
         run: |
-          IMAGE=ghcr.io/postalserver/postal
+          IMAGE=ghcr.io/${{ github.repository_owner }}/postal
 
           REF="${GITHUB_REF#refs/heads/}"
           if [ -z "$REF" ]; then exit 1; fi
 
-          VER="$(git describe --tags 2>/dev/null)"
+          # Sanitize branch name for Docker tags (replace / with -)
+          SAFE_REF="${REF//\//-}"
+
+          VER="$(git describe --tags 2>/dev/null || echo 'dev')"
           echo "version=${VER}" >> "$GITHUB_OUTPUT"
           echo "branch=${REF}" >> "$GITHUB_OUTPUT"
 
           echo 'tags<<EOF' >> "$GITHUB_OUTPUT"
           if [[ "$REF" == "main" ]]; then
             echo "${IMAGE}:latest" >> "$GITHUB_OUTPUT"
           else
-            echo "${IMAGE}:branch-${REF}" >> "$GITHUB_OUTPUT"
+            echo "${IMAGE}:branch-${SAFE_REF}" >> "$GITHUB_OUTPUT"
           fi
           echo 'EOF' >> "$GITHUB_OUTPUT"
       - uses: docker/build-push-action@v4
@@ -103,7 +107,7 @@ jobs:
           cache-from: type=gha
           cache-to: type=gha,mode=max
           target: full
-          platforms: linux/amd64
+          platforms: linux/amd64,linux/arm64
           build-args: |
             VERSION=${{ steps.info.outputs.version }}
             BRANCH=${{ steps.info.outputs.branch }}
@@ -126,11 +130,11 @@ jobs:
         with:
           push: true
           tags: |
-            ghcr.io/postalserver/postal:stable
-            ghcr.io/postalserver/postal:${{ needs.release-please.outputs.version }}
+            ghcr.io/${{ github.repository_owner }}/postal:stable
+            ghcr.io/${{ github.repository_owner }}/postal:${{ needs.release-please.outputs.version }}
           cache-from: type=gha
           cache-to: type=gha,mode=max
           target: full
           build-args: |
             VERSION=${{ needs.release-please.outputs.version }}
-          platforms: linux/amd64
+          platforms: linux/amd64,linux/arm64