Add Gitea Actions workflow to build and push the image on main

.gitea/workflows/deploy.yml

@@ -0,0 +1,54 @@
+# Builds the production image on every push to main and pushes it to the Gitea
+# registry, tagged with :latest AND the short commit SHA (for rollback) -- the
+# same tagging scheme as scripts/release.sh, but run by the act_runner instead
+# of by hand.
+#
+# It does NOT deploy: pulling and starting the new :latest on Unraid stays a
+# manual, deliberate step (Compose Down/Up). Auto-deploy via Watchtower is an
+# open item in docs/deployment.md and needs a health gate first, so a broken
+# page can never go live unnoticed.
+#
+# Required repository secrets (Gitea -> repo -> Settings -> Actions -> Secrets):
+#   REGISTRY_USER   the registry username (e.g. Tom)
+#   REGISTRY_TOKEN  a Gitea access token with package:write -- NOT the password
+
+name: Build and push image
+
+on:
+  push:
+    branches: [main]
+
+env:
+  IMAGE: gitea.anticarnist.de/tom/elternbeirat
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out the source
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to the Gitea registry
+        uses: docker/login-action@v3
+        with:
+          registry: gitea.anticarnist.de
+          username: ${{ secrets.REGISTRY_USER }}
+          password: ${{ secrets.REGISTRY_TOKEN }}
+
+      # The short SHA names the image content unambiguously and never moves,
+      # so it is the stable handle for a rollback.
+      - name: Compute the short commit SHA
+        id: sha
+        run: echo "short=$(git rev-parse --short HEAD)" >> "$GITHUB_OUTPUT"
+
+      - name: Build and push (:latest and :<sha>)
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: true
+          tags: |
+            ${{ env.IMAGE }}:latest
+            ${{ env.IMAGE }}:${{ steps.sha.outputs.short }}