👷 ci(build): enhance docker build process with buildx

- add Docker Buildx setup for advanced build capabilities
- update build step to use buildx for multi-platform support

.forgejo/workflows/build.yml

@@ -9,6 +9,9 @@ jobs:
   docker:
     runs-on: self-hosted
     steps:
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
       - name: Checkout
         uses: actions/checkout@v4
 
@@ -17,7 +20,8 @@ jobs:
 
       - name: Build image
         run: |
-          docker build -t "${{ secrets.REGISTRY_IMAGE }}:${{ github.sha }}" \
+          docker buildx build --load \
+            -t "${{ secrets.REGISTRY_IMAGE }}:${{ github.sha }}" \
             -t "${{ secrets.REGISTRY_IMAGE }}:latest" .
 
       - name: Push image