Add CI and multi-arch image publishing to GHCR

- CI workflow: go vet + build on push/PR.
- Docker workflow: build and push linux/amd64,arm64 to ghcr.io on main
  (:latest, :sha-<commit>) and on vX.Y.Z tags (:X.Y.Z, :X.Y, :X).
- Dockerfile cross-compiles per target arch for fast multi-arch builds.
- README: badges and published-image usage.

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

Author: Greg Maslowski

.github/workflows/ci.yml

@@ -0,0 +1,21 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version: "1.22"
+          cache: true
+      - run: go vet ./...
+      - run: go build ./...

.github/workflows/docker.yml

@@ -0,0 +1,52 @@
+name: Docker
+
+# Publishes a multi-arch image to GHCR.
+# - push to main        -> :latest and :sha-<commit>
+# - push a tag vX.Y.Z   -> :X.Y.Z, :X.Y, :X  (semantic version images)
+on:
+  push:
+    branches: [main]
+    tags: ["v*.*.*"]
+
+permissions:
+  contents: read
+  packages: write
+
+jobs:
+  image:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: docker/setup-qemu-action@v3
+      - uses: docker/setup-buildx-action@v3
+
+      - name: Log in to GHCR
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Derive tags and labels
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ghcr.io/${{ github.repository }}
+          tags: |
+            type=raw,value=latest,enable={{is_default_branch}}
+            type=sha
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=semver,pattern={{major}}
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max

Dockerfile

@@ -1,9 +1,11 @@
-# build
-FROM golang:1.22-alpine AS build
+# build (cross-compile from the native builder arch to the target arch)
+FROM --platform=$BUILDPLATFORM golang:1.22-alpine AS build
+ARG TARGETOS TARGETARCH
 WORKDIR /src
 RUN apk add --no-cache git
 COPY . .
-RUN go mod tidy && CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o /out/teslamate-dash .
+RUN go mod tidy && CGO_ENABLED=0 GOOS=$TARGETOS GOARCH=$TARGETARCH \
+    go build -trimpath -ldflags="-s -w" -o /out/teslamate-dash .
 
 # run (distroless, non-root, static)
 FROM gcr.io/distroless/static-debian12:nonroot

README.md

@@ -1,5 +1,9 @@
 # TeslaMate Dash
 
+[![CI](https://github.com/gmaslowski/teslamate-dash/actions/workflows/ci.yml/badge.svg)](https://github.com/gmaslowski/teslamate-dash/actions/workflows/ci.yml)
+[![Docker](https://github.com/gmaslowski/teslamate-dash/actions/workflows/docker.yml/badge.svg)](https://github.com/gmaslowski/teslamate-dash/actions/workflows/docker.yml)
+[![License: MIT](https://img.shields.io/badge/License-MIT-blue.svg)](LICENSE)
+
 A small, self-hosted, **read-only dashboard for [TeslaMate](https://github.com/teslamate-org/teslamate)**.
 It connects to your existing TeslaMate Postgres database and renders a clean, map-first view of your
 driving and charging history. One static Go binary, one container, no second database, and nothing is
@@ -39,6 +43,17 @@ Or with Go (1.22+):
 go run .          # demo mode when no DATABASE_HOST/TC_DSN is set
 ```
 
+### Published image
+
+Multi-arch images (linux/amd64 and linux/arm64) are published to GHCR on every release:
+
+```bash
+docker run --rm -p 4001:4001 ghcr.io/gmaslowski/teslamate-dash:latest
+# or pin a version: ghcr.io/gmaslowski/teslamate-dash:0.1.0
+```
+
+Tags: `latest` (tip of `main`), `X.Y.Z` / `X.Y` / `X` (semver from git tags), and `sha-<commit>`.
+
 ## Connect to your TeslaMate database
 
 Run it on the same Docker network as TeslaMate so it can reach Postgres. It reuses TeslaMate's