feat(ci): add the deploy job so the app deploys from the repo

The workflow built and pushed the image but never deployed it - the
cluster objects had been created by hand. This adds a `deploy` job that
applies the manifests in `kube/` and rolls the deployment.

The deploy job is separate from the build job on purpose. The
`KUBEC_CONFIG_BUILDX` secret is cluster-admin-equivalent, and a build step
that never talks to the cluster should not be able to read it.

Three things this job does that a naive `kubectl apply` does not:

1. `kubectl rollout restart`. The image tag is `:latest`, which is immutable
   in the manifest, so `apply` alone does not roll the pods. Without the
   restart the deployment reports success while the old pods keep serving
   the old image - a deploy that silently changes nothing.

2. Verifies the running digest against the registry's `:latest`. CI green and
   pods `Ready` do not prove the new code is live; the digest comparison does.

3. Smoke tests the running app - `/healthz` and `/readyz` - from inside the
   pod, so a deploy that comes up but cannot serve is caught in CI rather
   than by the next person to open the page.

The Secrets (`beer-db`, `beer-app`) are hand-provisioned and are deliberately
not in the apply set, so a deploy cannot clobber them.

.gitea/workflows/build_push.yml

@@ -93,3 +93,83 @@ jobs:
           platforms: linux/amd64
           tags: |
             git.aridgwayweb.com/armistace/beer-data:latest
+
+  # The deploy job is separate from the build job on purpose.  The
+  # `KUBEC_CONFIG_BUILDX` secret is cluster-admin-equivalent, and a build
+  # step that never talks to the cluster should not be able to read it - a
+  # compromised dependency in the build would otherwise have a direct path to
+  # the cluster.
+  deploy:
+    name: Deploy to the cluster
+    runs-on: ubuntu-latest
+    needs: build
+    if: gitea.ref == 'refs/heads/master'
+    timeout-minutes: 10
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Create Kubeconfig
+        run: |
+          mkdir -p $HOME/.kube
+          echo "${{ secrets.KUBEC_CONFIG_BUILDX }}" > $HOME/.kube/config
+
+      - name: Install kubectl
+        run: |
+          apt-get update
+          apt-get install -y apt-transport-https ca-certificates curl gnupg
+          curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.33/deb/Release.key | gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg
+          chmod 644 /etc/apt/keyrings/kubernetes-apt-keyring.gpg
+          echo 'deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.33/deb/ /' | tee /etc/apt/sources.list.d/kubernetes.list
+          apt-get update
+          apt-get install -y kubectl
+
+      - name: Deploy
+        run: |
+          # Apply the namespace and the non-secret manifests.  The Secrets
+          # (beer-db, beer-app) are hand-provisioned and are NOT in the repo,
+          # so they are deliberately not in the apply set.
+          kubectl apply -f kube/beer_namespace.yaml
+          kubectl apply -f kube/beer-deployment.yaml
+          kubectl apply -f kube/beer-service.yaml
+
+          # The image tag is `:latest`, which is immutable in the manifest, so
+          # `kubectl apply` alone does NOT roll the pods.  Without the restart
+          # the deployment reports success while the old pods keep serving
+          # the old image.
+          kubectl -n beer rollout restart deployment/beer-deployment
+          kubectl -n beer rollout status deployment/beer-deployment --timeout=180s
+
+      - name: Verify the new image is actually running
+        run: |
+          # CI green and pods Ready do NOT prove the new code is live.  Compare
+          # the running digest against the registry's :latest.
+          RUNNING=$(kubectl -n beer get pod -l app=beer-data \
+            -o jsonpath='{.items[0].status.containerStatuses[0].imageID}')
+          REGISTRY=$(curl -s -u "armistace:${{ secrets.REG_PASSWORD }}" -I \
+            "https://git.aridgwayweb.com/v2/armistace/beer-data/manifests/latest" \
+            -H "Accept: application/vnd.docker.distribution.manifest.v2+json" \
+            | grep -i docker-content-digest | awk '{print $2}' | tr -d '\r')
+          echo "running:  $RUNNING"
+          echo "registry: $REGISTRY"
+          if [ "$RUNNING" != "$REGISTRY" ]; then
+            echo "ERROR: the running pod is not the image that was just pushed"
+            exit 1
+          fi
+
+      - name: Smoke test the deployed app
+        run: |
+          # The pods are behind a NodePort.  Hit the service directly from
+          # inside the cluster.
+          for i in $(seq 1 12); do
+            if kubectl -n beer exec deploy/beer-deployment -- \
+                python -c "import urllib.request,sys; sys.exit(0 if urllib.request.urlopen('http://127.0.0.1:5000/healthz').status==200 else 1)"; then
+              echo "healthz OK"
+              break
+            fi
+            echo "waiting for the app to come up ($i/12)"
+            sleep 5
+          done
+          kubectl -n beer exec deploy/beer-deployment -- \
+            python -c "import urllib.request,sys; r=urllib.request.urlopen('http://127.0.0.1:5000/readyz'); print('readyz:', r.read().decode()); sys.exit(0 if r.status==200 else 1)"