ci: auto build multi-arch image to GHCR with cleanup

.github/workflows/docker.yml

@@ -0,0 +1,148 @@
+name: Docker
+
+on:
+  push:
+    branches: [main]
+    tags: ['v*']
+    paths-ignore: ['**.md', 'docs/**']
+  pull_request:
+    branches: [main]
+  workflow_dispatch:
+    inputs:
+      keep-images:
+        description: "Untagged image versions to keep"
+        default: "2"
+      keep-runs:
+        description: "Workflow runs to keep"
+        default: "1"
+
+# Cancel superseded runs on the same ref to save minutes.
+concurrency:
+  group: docker-${{ github.ref }}
+  cancel-in-progress: true
+
+env:
+  IMAGE: ghcr.io/${{ github.repository }}
+  KEEP_IMAGES: ${{ github.event.inputs.keep-images || 2 }}
+  KEEP_RUNS: ${{ github.event.inputs.keep-runs || 1 }}
+
+jobs:
+  # Build each arch on its native runner (no QEMU emulation).
+  build:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - platform: linux/amd64
+            runner: ubuntu-latest
+            suffix: amd64
+          - platform: linux/arm64
+            runner: ubuntu-24.04-arm
+            suffix: arm64
+    runs-on: ${{ matrix.runner }}
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - uses: actions/checkout@v4
+      - uses: docker/setup-buildx-action@v3
+
+      - name: Log in to GHCR
+        if: github.event_name != 'pull_request'
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build image
+        id: build
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          platforms: ${{ matrix.platform }}
+          outputs: type=image,name=${{ env.IMAGE }},push-by-digest=true,name-canonical=true,push=${{ github.event_name != 'pull_request' }}
+          build-args: |
+            VERSION=${{ github.ref_type == 'tag' && github.ref_name || github.sha }}
+            COMMIT=${{ github.sha }}
+          cache-from: type=gha,scope=build-${{ matrix.suffix }}
+          cache-to: type=gha,mode=max,scope=build-${{ matrix.suffix }}
+
+      - name: Export digest
+        if: github.event_name != 'pull_request'
+        env:
+          DIGEST: ${{ steps.build.outputs.digest }}
+        run: |
+          mkdir -p "${RUNNER_TEMP}/digests"
+          test -n "${DIGEST}"
+          touch "${RUNNER_TEMP}/digests/${DIGEST#sha256:}"
+
+      - uses: actions/upload-artifact@v4
+        if: github.event_name != 'pull_request'
+        with:
+          name: digests-${{ matrix.suffix }}
+          path: ${{ runner.temp }}/digests/*
+          if-no-files-found: error
+          retention-days: 1
+
+  # Merge per-arch images into one manifest list, then prune old versions/runs.
+  merge:
+    if: github.event_name != 'pull_request'
+    needs: build
+    runs-on: ubuntu-latest
+    permissions:
+      actions: write
+      contents: read
+      packages: write
+    steps:
+      - uses: actions/download-artifact@v4
+        with:
+          path: ${{ runner.temp }}/digests
+          pattern: digests-*
+          merge-multiple: true
+
+      - uses: docker/setup-buildx-action@v3
+
+      - name: Log in to GHCR
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.IMAGE }}
+          tags: |
+            type=raw,value=latest,enable={{is_default_branch}}
+            type=ref,event=branch
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=sha,prefix=,suffix=,format=short
+
+      - name: Create manifest list and push
+        working-directory: ${{ runner.temp }}/digests
+        env:
+          META_JSON: ${{ steps.meta.outputs.json }}
+        run: |
+          # shellcheck disable=SC2046 # unquoted on purpose: expand each digest into a separate arg
+          jq -j '.tags[] | "-t", "\u0000", ., "\u0000"' <<< "${META_JSON}" \
+            | xargs -0 docker buildx imagetools create $(printf "${IMAGE}@sha256:%s " *)
+
+      # Keeps the latest multi-arch image plus its per-arch manifests.
+      # Pinned: actions/delete-package-versions@v5 (official, v5.0.0).
+      - uses: actions/delete-package-versions@e5bc658cc4c965c472efe991f8beea3981499c55
+        with:
+          package-name: fenfa
+          package-type: container
+          min-versions-to-keep: ${{ env.KEEP_IMAGES }}
+          delete-only-untagged-versions: "true"
+
+      # Keeps the latest run (this one, still in progress) and older runs only.
+      # Pinned: Mattraks/delete-workflow-runs@v2 (v2 -> v2.1.0, latest commit 2026-06-05).
+      - uses: Mattraks/delete-workflow-runs@0cf693bc9909e5e867ee8f27b813224ba862939c
+        with:
+          retain_days: 0
+          keep_minimum_runs: ${{ env.KEEP_RUNS }}

Dockerfile

@@ -1,24 +1,41 @@
+# syntax=docker/dockerfile:1
 # Multi-stage, multi-arch build for fenfa
 # Frontend build (Node)
-FROM node:20-alpine AS node-builder
+# NOTE: frontend output is arch-independent static files, so always build it
+# on the native runner arch ($BUILDPLATFORM) to avoid QEMU SIGILL (exit 132)
+# caused by vite/rollup native binaries under arm64 emulation.
+FROM --platform=$BUILDPLATFORM node:20-alpine AS node-builder
 WORKDIR /src
+# Copy manifests first so npm install layers stay cached across code changes
+COPY web/front/package.json web/front/package-lock.json ./web/front/
+COPY web/admin/package.json web/admin/package-lock.json ./web/admin/
+RUN --mount=type=cache,target=/root/.npm \
+    cd web/front && npm ci --no-audit --no-fund \
+    && cd ../admin && npm ci --no-audit --no-fund
 COPY . .
 # Build front and admin (vite)
-RUN cd web/front && npm install && npm run build
-RUN cd web/admin && npm install && npm run build
+RUN cd web/front && npm run build
+RUN cd web/admin && npm run build
 
 # Go build (needs CGO + sqlite headers)
 FROM golang:1.25-alpine AS go-builder
 RUN apk add --no-cache build-base sqlite-dev
 ENV CGO_ENABLED=1
 WORKDIR /src
+# Copy go manifests first so module download stays cached across code changes
+COPY go.mod go.sum ./
+RUN --mount=type=cache,target=/go/pkg/mod \
+    --mount=type=cache,target=/root/.cache/go-build \
+    go mod download
 COPY . .
 # Bring in the built frontend artifacts from node-builder stage
 COPY --from=node-builder /src/internal/web/dist /src/internal/web/dist
 # Build server binary
 ARG VERSION=dev
 ARG COMMIT=none
-RUN go build -ldflags="-s -w -X main.version=${VERSION} -X main.commit=${COMMIT}" -o /out/fenfa ./cmd/server
+RUN --mount=type=cache,target=/go/pkg/mod \
+    --mount=type=cache,target=/root/.cache/go-build \
+    go build -ldflags="-s -w -X main.version=${VERSION} -X main.commit=${COMMIT}" -o /out/fenfa ./cmd/server
 
 # Runtime image
 FROM alpine:3.22.2