Added workflow for docker containers

.dockerignore

@@ -0,0 +1,7 @@
+.git
+.gitea
+.claude
+.github
+dist
+*.md
+install.sh

.gitea/workflows/container.yaml

@@ -0,0 +1,73 @@
+name: Container image
+
+# Builds the multi-arch container image. On tag push (v*) it logs in
+# to the Gitea registry on this host and publishes the image as
+# git.cer.sh/<owner>/<repo>:<version> plus :latest. On pull requests
+# it builds without pushing — purely a smoke test that the Dockerfile
+# still works.
+on:
+  push:
+    tags:
+      - 'v*'
+  pull_request:
+
+permissions:
+  contents: read
+  packages: write
+
+jobs:
+  image:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Buildx
+        uses: docker/setup-buildx-action@v3
+
+      # github.repository is owner/name with the repo's original casing;
+      # registries require lowercase, so normalise once here and reuse
+      # the result in metadata-action below.
+      - name: Resolve image name
+        id: img
+        run: |
+          repo='${{ github.repository }}'
+          echo "ref=git.cer.sh/${repo,,}" >> "$GITHUB_OUTPUT"
+
+      - name: Login to Gitea registry
+        if: github.event_name == 'push'
+        uses: docker/login-action@v3
+        with:
+          registry: git.cer.sh
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Docker metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ steps.img.outputs.ref }}
+          tags: |
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=raw,value=latest,enable=${{ startsWith(github.ref, 'refs/tags/v') }}
+
+      - name: Build (and push on tag)
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: ./Dockerfile
+          platforms: linux/amd64,linux/arm64
+          push: ${{ github.event_name == 'push' }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          build-args: |
+            VERSION=${{ github.ref_name }}
+          # Inline cache embeds layer metadata into the pushed image
+          # itself — no external cache server needed, which keeps the
+          # workflow self-contained on the Gitea runner.
+          cache-from: type=inline
+          cache-to: type=inline

Dockerfile

@@ -0,0 +1,41 @@
+# syntax=docker/dockerfile:1.7
+
+# Build stage. Runs on the runner's native arch (BUILDPLATFORM) and
+# cross-compiles the Go binary for whichever target the manifest list
+# is being assembled for (TARGETOS/TARGETARCH). Keeps multi-arch
+# builds fast — only the final link is per-arch, the Go toolchain is
+# always native.
+FROM --platform=$BUILDPLATFORM golang:1.24-alpine AS builder
+ARG TARGETOS
+ARG TARGETARCH
+ARG VERSION=dev
+
+WORKDIR /src
+
+# Module cache layer — re-uses unless go.mod/go.sum change.
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+
+RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} \
+    go build \
+      -trimpath \
+      -ldflags "-s -w -X main.version=${VERSION}" \
+      -o /out/qu \
+      ./cmd/qu
+
+# Runtime stage. distroless/static has CA roots for HTTPS probes and
+# nothing else — no shell, no package manager. Runs as root so the
+# daemon can open ICMP sockets and write under /etc/quptime; operators
+# can override at deploy time with `docker run --user`.
+FROM gcr.io/distroless/static-debian12:latest
+
+COPY --from=builder /out/qu /usr/local/bin/qu
+
+ENV QUPTIME_DIR=/etc/quptime
+VOLUME ["/etc/quptime"]
+EXPOSE 9901
+
+ENTRYPOINT ["/usr/local/bin/qu"]
+CMD ["serve"]