fix(ci): fix broken Docker workflow and modernize (#1318)

* fix(ci): fix broken Docker workflow and modernize

## Critical Bug Fixes

1. **Fix broken push condition** (CRITICAL):
   - Old: `push: ${{ github.ref == 'refs/heads/master' }}`
   - Problem: Branch renamed to `main`, so images NEVER pushed
   - New: `push: ${{ github.event_name != 'pull_request' }}`
   - Result: Docker images will actually be published again

2. **Add missing checkout step**:
   - Build was failing because source code wasn't checked out
   - Required for Docker build context

## Modernization Improvements

3. **Migrate to GitHub Container Registry (GHCR)**:
   - Old: DockerHub with `DOCKERHUB_USERNAME` and `DOCKERHUB_TOKEN` secrets
   - New: GHCR with built-in `GITHUB_TOKEN`
   - Benefits: No external account required, better integration

4. **Add semantic versioning**:
   - Automatically tags releases: `v1.2.3`, `v1.2`, `v1`, `latest`
   - Supports version tags (v*), branches, and PRs
   - Uses docker/metadata-action for automatic tagging

5. **Add GitHub Actions caching**:
   - Uses `type=gha` cache for faster builds
   - Reduces build times and GitHub Actions minutes

6. **Security: Digest pinning**:
   - All actions pinned to commit SHAs
   - Prevents supply chain attacks via tag manipulation
   - Follows security best practices

7. **Add explicit permissions**:
   - Minimal required permissions (contents: read, packages: write)
   - Follows principle of least privilege

8. **Add workflow triggers**:
   - Tags (v*) for releases
   - Pull requests for testing
   - Manual dispatch for on-demand builds

## Testing

- Workflow syntax validated
- Push logic tested with different event types
- Compatible with existing Docker build process

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* refactor(ci): simplify docker workflow

- Use version tags instead of SHA pins for readability
- Remove verbose step names (action names are self-documenting)
- Compact YAML formatting
- Fix actions/checkout to v4 (v6 doesn't exist)

---------

Co-authored-by: Bas Nijholt <bas@nijho.lt>

.github/workflows/docker-build.yml

@@ -1,32 +1,50 @@
-name: docker
+name: Docker
 
 on:
   push:
-    branches:
-      - "main"
+    branches: [main]
+    tags: ['v*']
+  pull_request:
+  workflow_dispatch:
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
 
 jobs:
-  docker:
+  build:
     runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
     strategy:
       matrix:
-        platform:
-          - linux/amd64
-          - linux/arm64
+        platform: [linux/amd64, linux/arm64]
     steps:
-      - name: Set up QEMU
-        uses: docker/setup-qemu-action@v3
-      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3
-      - name: Login to Docker Hub
-        uses: docker/login-action@v3
+      - uses: actions/checkout@v4
+      - uses: docker/setup-qemu-action@v3
+      - uses: docker/setup-buildx-action@v3
+      - uses: docker/login-action@v3
         with:
-          username: ${{ secrets.DOCKERHUB_USERNAME }}
-          password: ${{ secrets.DOCKERHUB_TOKEN }}
-      - name: Build and push
-        uses: docker/build-push-action@v6
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - id: meta
+        uses: docker/metadata-action@v5
         with:
-          # Only push on the master branch
-          push: ${{ github.ref == 'refs/heads/master' }}
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=ref,event=branch
+            type=ref,event=pr
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=raw,value=latest,enable={{is_default_branch}}
+      - uses: docker/build-push-action@v6
+        with:
+          context: .
           platforms: ${{ matrix.platform }}
-          tags: ${{ secrets.DOCKERHUB_USERNAME }}/adaptive-lighting:latest
+          push: ${{ github.event_name != 'pull_request' }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max