ci: docker publish workflow for indexer-api + indexer-worker images (#52)

Builds + pushes both images to Docker Hub on every git tag (v*).
Operators that want to self-host the Sentrix indexer get a clean path:

  docker pull sentriscloud/indexer-api:0.4.0
  docker pull sentriscloud/indexer-worker:0.4.0

vs the current path of cloning the repo + pnpm install + docker
compose build. :latest tag tracks the highest non-prerelease semver.

Matrix builds api + worker in parallel using docker buildx with GHA
cache (per-image scope so api builds don't invalidate worker cache).
linux/amd64 only for now — arm64 emulation runs ~5x slower on x86
runners; opt in via a follow-up workflow when there's actual demand.

Manual workflow_dispatch path for ad-hoc rebuilds (eg base-image
security bump that doesn't ship a code change). Requires
DOCKERHUB_USERNAME + DOCKERHUB_TOKEN repo secrets — add via
Settings → Secrets and variables → Actions before tagging the first
release.

Image labels follow OCI spec — source / revision / version / license
so registries that index labels (Docker Hub UI, GHCR, Artifact
Hub) display the right metadata.

Author: satyakwok

.github/workflows/docker-publish.yml

@@ -0,0 +1,105 @@
+name: docker publish
+
+# Builds + pushes the api and worker images to Docker Hub on every git
+# tag of the form v* (eg v0.4.0, v0.4.1-rc.0). Tags are derived from
+# the git tag so consumers can pin precisely:
+#
+#   docker pull sentriscloud/indexer-api:0.4.0
+#   docker pull sentriscloud/indexer-worker:0.4.0
+#
+# `latest` is also pushed when the tag is a non-prerelease semver (no
+# hyphen suffix), so `:latest` always points at a stable release.
+#
+# Manual workflow_dispatch is allowed for ad-hoc rebuilds (eg after a
+# base-image security bump that doesn't ship a code change). The
+# operator picks which tag to rebuild via the input.
+
+on:
+  push:
+    tags:
+      - 'v*'
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: 'git tag to rebuild (eg v0.4.0)'
+        required: true
+        type: string
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    name: build + push (${{ matrix.image }})
+    runs-on: ubuntu-22.04
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - image: indexer-api
+            dockerfile: apps/api/Dockerfile
+          - image: indexer-worker
+            dockerfile: apps/indexer/Dockerfile
+    steps:
+      - uses: actions/checkout@v5
+        with:
+          ref: ${{ inputs.tag || github.ref }}
+
+      - uses: docker/setup-qemu-action@v3
+      - uses: docker/setup-buildx-action@v3
+
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Resolve version tag
+        id: ver
+        run: |
+          REF="${{ inputs.tag || github.ref_name }}"
+          # Strip leading 'v' so the docker tag matches semver convention.
+          VERSION="${REF#v}"
+          echo "version=$VERSION" >> $GITHUB_OUTPUT
+          # Push :latest only on non-prerelease (no '-' suffix).
+          if [[ "$VERSION" != *-* ]]; then
+            echo "latest=true" >> $GITHUB_OUTPUT
+          else
+            echo "latest=false" >> $GITHUB_OUTPUT
+          fi
+
+      - name: Compose docker tags
+        id: tags
+        run: |
+          TAGS="sentriscloud/${{ matrix.image }}:${{ steps.ver.outputs.version }}"
+          if [ "${{ steps.ver.outputs.latest }}" = "true" ]; then
+            TAGS="$TAGS,sentriscloud/${{ matrix.image }}:latest"
+          fi
+          # Multi-line for buildx --tag flag.
+          {
+            echo 'tags<<EOF'
+            echo "$TAGS" | tr ',' '\n'
+            echo 'EOF'
+          } >> $GITHUB_OUTPUT
+
+      - name: Build + push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: ${{ matrix.dockerfile }}
+          push: true
+          # linux/amd64 only for now — arm64 build infrastructure
+          # (qemu emulation on x86 runners) takes ~5x longer; opt in
+          # via a follow-up workflow when arm64 demand surfaces.
+          platforms: linux/amd64
+          tags: ${{ steps.tags.outputs.tags }}
+          labels: |
+            org.opencontainers.image.source=https://github.com/${{ github.repository }}
+            org.opencontainers.image.revision=${{ github.sha }}
+            org.opencontainers.image.version=${{ steps.ver.outputs.version }}
+            org.opencontainers.image.licenses=MIT
+          cache-from: type=gha,scope=${{ matrix.image }}
+          cache-to: type=gha,mode=max,scope=${{ matrix.image }}
+
+      - name: Image digest
+        run: echo "${{ matrix.image }}:${{ steps.ver.outputs.version }} → built + pushed"