ci: build multi-arch images (amd64, arm64, arm/v7)

- Add QEMU for cross-platform emulation
- Add Docker Buildx for multi-platform builds
- Build for linux/amd64, linux/arm64, linux/arm/v7

.gitea/workflows/build-image.yml

@@ -22,11 +22,18 @@ jobs:
           echo "release=${RELEASE_NAME}" >> $GITHUB_OUTPUT
           echo "Building version ${VERSION} from branch ${BRANCH}"
 
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
       - name: Build and push Docker image
         uses: docker/build-push-action@v5
         with:
           context: .
           push: true
+          platforms: linux/amd64,linux/arm64,linux/arm/v7
           tags: |
             reg.i3omb.com/sofarr:${{ steps.version.outputs.version }}
             reg.i3omb.com/sofarr:${{ steps.version.outputs.release }}