ci(alpha): move from docker hub to ghcr.io registry

.github/workflows/alpha-release.yml

@@ -40,11 +40,12 @@ jobs:
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
-      - name: Login to DockerHub
+      - name: Login to GitHub Container Registry
         uses: docker/login-action@v3
         with:
-          username: ${{ secrets.DOCKERHUB_USERNAME }}
-          password: ${{ secrets.DOCKERHUB_TOKEN }}
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Build and push images
         uses: docker/build-push-action@v5
@@ -52,9 +53,9 @@ jobs:
           context: .
           platforms: linux/amd64,linux/arm64
           push: true
-          tags: meienberger/runtipi:${{ needs.create-tag.outputs.tagname }}
-          cache-from: type=registry,ref=meienberger/runtipi:buildcache
-          cache-to: type=registry,ref=meienberger/runtipi:buildcache,mode=max
+          tags: ghcr.io/${{ github.repository_owner }}/runtipi:${{ needs.create-tag.outputs.tagname }}
+          cache-from: type=registry,ref=ghcr.io/${{ github.repository_owner }}/runtipi:buildcache
+          cache-to: type=registry,ref=ghcr.io/${{ github.repository_owner }}/runtipi:buildcache,mode=max
 
   build-cli:
     runs-on: ubuntu-latest