Refactor registry handling in Docker workflow to use RUNNER_REGISTRY environment variable

Signed-off-by: Stephen Simpson <ssimpson89@users.noreply.github.com>

.gitea/workflows/docker-image-linux.yml

@@ -15,16 +15,27 @@ env:
 jobs:
   build-and-push:
     runs-on: ubuntu-latest
-    env:
-      REGISTRY: ${{ runner.labels.filter(l => l.startsWith('registry=')).map(l => l.split('=')[1]).first() || 'gitea.sjs.io' }}
-    container:
-      image: gitea/runner-images:ubuntu-latest
 
     permissions:
       contents: read
       packages: write
 
     steps:
+      - name: Get Registry
+        id: registry
+        run: |
+          # Use RUNNER_REGISTRY environment variable
+          if [ ! -z "${RUNNER_REGISTRY}" ]; then
+            REGISTRY="${RUNNER_REGISTRY}"
+          else
+            echo "ERROR: RUNNER_REGISTRY environment variable not set"
+            echo "Please add RUNNER_REGISTRY to your runner's environment variables"
+            exit 1
+          fi
+          
+          echo "registry=${REGISTRY}" >> $GITHUB_OUTPUT
+          echo "Using registry: ${REGISTRY}"
+
       - name: Checkout code
         uses: actions/checkout@v4
 
@@ -37,7 +48,7 @@ jobs:
       - name: Log in to registry
         uses: docker/login-action@v3
         with:
-          registry: ${{ env.REGISTRY }}
+          registry: ${{ steps.registry.outputs.registry }}
           username: ${{ vars.USERNAME }}
           password: ${{ secrets.PASS }}
 
@@ -45,7 +56,7 @@ jobs:
         id: meta
         uses: docker/metadata-action@v5
         with:
-          images: ${{ env.REGISTRY }}/${{ vars.USERNAME }}/${{ env.IMAGE_NAME }}
+          images: ${{ steps.registry.outputs.registry }}/${{ vars.USERNAME }}/${{ env.IMAGE_NAME }}
           tags: |
             # Only tag with version and latest on tag push
             type=semver,pattern={{version}},enable=${{ startsWith(github.ref, 'refs/tags/') }}