ci: build via host docker socket (plain build); fix missing daemon socket

build-and-push failed at docker/setup-buildx-action: the job had no
/var/run/docker.sock, so buildx's docker-container driver couldn't reach
the daemon. Mount the host socket into build-and-push and deploy, and
replace setup-buildx + build-push-action (+ the unsupported gha cache)
with a plain docker build/push against the host daemon (DooD), reusing
the host's layer cache.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitea/workflows/deploy.yml

@@ -72,9 +72,17 @@ jobs:
     runs-on: ubuntu-latest
     needs: [test-backend, test-frontend]
     # PRs only run the test jobs; build + deploy are reserved for
-    # post-merge pushes to main. Without this gate every PR would push
-    # a tagged image to the registry and SSH-deploy to prod.
+    # post-merge pushes to main.
     if: github.event_name != 'pull_request'
+    # Build on the host docker daemon directly (docker-outside-of-docker):
+    # the runner shares the deploy host's daemon, so a plain `docker build`
+    # reuses the host's layer cache and avoids buildx's docker-container
+    # driver + the gha cache exporter — neither works against this single-host
+    # act_runner, and there is no in-job daemon socket unless we mount it.
+    container:
+      image: docker.gitea.com/runner-images:ubuntu-latest
+      volumes:
+        - /var/run/docker.sock:/var/run/docker.sock
     outputs:
       image_tag: ${{ steps.meta.outputs.image_tag }}
       version: ${{ steps.meta.outputs.version }}
@@ -93,48 +101,32 @@ jobs:
           echo "image_tag=${GITHUB_SHA}" >> "$GITHUB_OUTPUT"
           echo "version=${version}" >> "$GITHUB_OUTPUT"
 
-      - uses: docker/setup-buildx-action@v3
-
-      - name: docker login
-        uses: docker/login-action@v3
-        with:
-          registry: ${{ secrets.REGISTRY_URL }}
-          username: ${{ secrets.REGISTRY_USERNAME }}
-          password: ${{ secrets.REGISTRY_PASSWORD }}
-
-      - name: Build & push backend
-        uses: docker/build-push-action@v5
-        with:
-          context: ./backend
-          push: true
-          tags: |
-            ${{ secrets.REGISTRY_URL }}/mangalord-backend:latest
-            ${{ secrets.REGISTRY_URL }}/mangalord-backend:${{ steps.meta.outputs.image_tag }}
-            ${{ secrets.REGISTRY_URL }}/mangalord-backend:${{ steps.meta.outputs.version }}
-          cache-from: type=gha,scope=backend
-          cache-to: type=gha,mode=max,scope=backend
-
-      - name: Build & push frontend
-        uses: docker/build-push-action@v5
-        with:
-          context: ./frontend
-          push: true
-          tags: |
-            ${{ secrets.REGISTRY_URL }}/mangalord-frontend:latest
-            ${{ secrets.REGISTRY_URL }}/mangalord-frontend:${{ steps.meta.outputs.image_tag }}
-            ${{ secrets.REGISTRY_URL }}/mangalord-frontend:${{ steps.meta.outputs.version }}
-          cache-from: type=gha,scope=frontend
-          cache-to: type=gha,mode=max,scope=frontend
+      - name: Build & push backend + frontend
+        env:
+          REGISTRY_URL: ${{ secrets.REGISTRY_URL }}
+          REGISTRY_USERNAME: ${{ secrets.REGISTRY_USERNAME }}
+          REGISTRY_PASSWORD: ${{ secrets.REGISTRY_PASSWORD }}
+          IMAGE_TAG: ${{ steps.meta.outputs.image_tag }}
+          VERSION: ${{ steps.meta.outputs.version }}
+        run: |
+          set -eu
+          echo "$REGISTRY_PASSWORD" | docker login "$REGISTRY_URL" -u "$REGISTRY_USERNAME" --password-stdin
+          for svc in backend frontend; do
+            img="$REGISTRY_URL/mangalord-$svc"
+            docker build -t "$img:$IMAGE_TAG" -t "$img:latest" -t "$img:$VERSION" "./$svc"
+            for tag in "$IMAGE_TAG" latest "$VERSION"; do docker push "$img:$tag"; done
+          done
+          docker logout "$REGISTRY_URL"
 
   deploy:
     runs-on: ubuntu-latest
     needs: build-and-push
     if: github.event_name != 'pull_request'
     # Single-host deploy: the runner lives on the same box as the stack, so we
-    # drive the host docker daemon directly (act_runner shares its socket via
-    # `docker_host: "-"`) instead of SSHing out. The compose dir is bind-mounted
-    # at its REAL host path so compose's relative bind-mounts (./mangalord/...,
-    # ./Caddyfile) resolve; this requires `/mnt/ssd/docker-data` in the runner's
+    # drive the host docker daemon directly (the job mounts the host docker
+    # socket) instead of SSHing out. The compose dir is bind-mounted at its
+    # REAL host path so compose's relative bind-mounts (./mangalord/...,
+    # ./Caddyfile) resolve; both paths must be in the runner's
     # container.valid_volumes. The central compose references the images as
     # registry.mc02.dev/mangalord-*:${MANGALORD_TAG:-latest}, so we only pull
     # and recreate the two mangalord services at the freshly built SHA.
@@ -142,6 +134,7 @@ jobs:
       image: docker:cli
       volumes:
         - /mnt/ssd/docker-data:/mnt/ssd/docker-data
+        - /var/run/docker.sock:/var/run/docker.sock
     steps:
       - name: Deploy to the local stack
         working-directory: /mnt/ssd/docker-data