ci: use podman instead of docker for container builds

.gitea/workflows/ci.yaml

@@ -1,32 +1,27 @@
-name: Container build
+name: Build container
 on:
   push:
   schedule:
     - cron: '0 16 * * FRI'
 
 jobs:
-  container-build:
-    runs-on: citadel
-    if: gitea.ref == 'refs/heads/main'
-    env:
-      RUNNER_TOOL_CACHE: /toolcache
+  build:
+    runs-on: rocky-minimal
     steps:
-      - name: Clone repo
-        uses: actions/checkout@v4
-      - name: Set up BuildX
-        uses: docker/setup-buildx-action@v2
+      - uses: actions/checkout@v4
+      - name: Build
+        uses: redhat-actions/buildah-build@v2
         with:
-          endpoint: 'unix:///var/run/docker.sock'
-      - name: Login to Registry
-        uses: docker/login-action@v3
+          image: ${{ github.actor }}/${{ github.event.repository.name }}
+          tags: latest
+          containerfiles: |
+            ./Containerfile
+      - name: Push
+        uses: redhat-actions/push-to-registry@v2
         with:
+          image: ${{ github.actor }}/${{ github.event.repository.name }}
+          tags: latest
+          extra-args: --compression-format zstd:chunked
           registry: git.plabble.org
           username: ${{ secrets.REGISTRY_USERNAME }}
           password: ${{ secrets.REGISTRY_TOKEN }}
-      - name: Build and push
-        uses: docker/build-push-action@v6
-        with:
-          context: .
-          file: ./Containerfile
-          push: true
-          tags: git.plabble.org/job79/dev:latest