feat(ci): add GitHub Actions workflow for Docker image build and push

- Create a new workflow to build and push Docker images for backend and frontend applications to GitHub Container Registry
- Configure steps for checking out the repository, setting up Docker Buildx, logging in to the registry, extracting metadata, and building/pushing images

Author: marcuwynu23

.github/workflows/docker-publish.yml

@@ -0,0 +1,61 @@
+name: Build and push Docker images to GHCR
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+env:
+  REGISTRY: ghcr.io
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    strategy:
+      matrix:
+        include:
+          - name: backend
+            dockerfile: apps/backend/Dockerfile
+            image: repohub-backend
+          - name: frontend
+            dockerfile: apps/frontend/Dockerfile
+            image: repohub-frontend
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata (tags, labels)
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ github.repository_owner }}/${{ matrix.image }}
+          tags: |
+            type=ref,event=branch
+            type=sha,prefix=
+            type=raw,value=latest,enable=${{ github.ref == 'refs/heads/main' }}
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: ${{ matrix.dockerfile }}
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max